Introduction

Medicinal and aromatic plants (MAPs) are cornerstone crops in many agroecosystems, valued for their essential oils, bioactive compounds, and high economic returns per unit area1,2. In climate-sensitive regions such as North Africa and the Middle East, MAPs also present opportunities for climate-smart agriculture by contributing to carbon sequestration and oxygen production while supporting diversified rural livelihoods3,4. The global essential oil market, estimated at USD 10.47 billion in 2022, is projected to reach USD 22.41 billion by 2030, reflecting growing demand across pharmaceutical, cosmetic, and food industries5,6.

However, climate change poses significant threats to MAP cultivation and quality. Recent meta-analyses demonstrate that elevated temperatures, altered precipitation patterns, and increased CO₂ concentrations systematically affect secondary metabolite profiles, phenology, and geographic distribution of medicinal plants1,7. Studies across Mediterranean and Himalayan regions predict range contractions for several MAP species under future climate scenarios, with potential declines in suitable habitat area of 20–60% by 20508,9. These shifts threaten both wild populations and agricultural production systems, emphasizing the urgency of integrating climate considerations into MAP value chain assessments10,11.

Steam distillation remains the dominant industrial extraction pathway, accounting for over 90% of global essential oil output, thereby linking the environmental performance of MAP value chains to the energy intensity of thermal processes12,13. Recent life cycle assessment (LCA) studies consistently identify distillation energy as the principal environmental hotspot in essential oil production. For rosemary in Portugal, hydrodistillation accounted for 166–363 MJ per gram of aromatic extract, with cumulative emissions of 8.8–19.3 kg CO₂-eq depending on feedstock moisture content12. Similar LCA analyses for lavender, eucalyptus, and rose oil report thermal energy contributions of 60–85% to total carbon footprints14,15.

Technological responses increasingly target the energy bottleneck in hydrodistillation. Solar thermal technologies—including Scheffler concentrators, parabolic troughs, and linear Fresnel collectors—have been piloted to provide process steam for essential oil extraction, demonstrating fuel substitutions of 40–100% and greenhouse gas reductions of 35–75% compared to conventional fossil fuel systems16,17. Recent pilot studies in India achieved solar distillation efficiencies of 27–33% with steam production rates of 2 kg/h at solar insolation levels of 700–850 W/m²17. Economic analyses indicate benefit-cost ratios of 1.5–1.8 and payback periods of 18–24 months for solar-assisted extraction systems, confirming technical and financial viability18.

At the farm gate, oxygen production and carbon uptake are functions of canopy development, photosynthetic efficiency, and cropping calendars19. Despite MAPs’ recognized role in ecosystem services provision, systematic quantification of their net climate impact—integrating both cultivation-phase carbon sequestration and processing-phase emissions—remains scarce in the literature. Country-specific electricity emission factors strongly condition the irrigation footprint; in many emerging economies these often exceed 0.45–0.60 kg CO₂/kWh, making efficient water management and solar pumping priorities for footprint reduction4,20.

Within this context, Egypt is strategically positioned as a global exporter of essential oils (e.g., geranium, jasmine, basil) and a living laboratory for sustainability transitions in MAP value chains21. Aromatic plants constitute important economic crops in Egypt and represent a main source of farmers’ income in several governorates22,23,24. However, comprehensive environmental assessments integrating cultivation, extraction, and net carbon balance for Egyptian MAP systems are lacking.

This study addresses this research gap by conducting cradle-to-gate life cycle assessments of two commercially important MAPs cultivated in Egypt: Pelargonium graveolens (geranium) and Viola odorata (violet). We quantify oxygen production, photosynthetic CO₂ sequestration, and net greenhouse gas footprints per functional unit (per feddan and per kg product), compare environmental performance across species and extraction methods, and evaluate decarbonization scenarios incorporating solar thermal and biogas substitution. This research contributes quantitative evidence for prioritizing low-emission extraction technologies and positioning MAPs as climate-smart crops within Egypt’s agricultural diversification strategy.

Materials and methods

Goal and scope definition

This study followed the ISO 14040:2006 and ISO 14044:2006 framework for life cycle assessment (International Organization for Standardization [ISO], 2006a, 2006b). The goal was to compare the environmental performance of two medicinal and aromatic plant (MAP) systems, Pelargonium graveolens (geranium) and Viola odorata (violet), cultivated under Egyptian conditions, with specific focus on oxygen production, photosynthetic CO₂ sequestration, and net greenhouse gas (GHG) footprint. Two functional units were employed to enable comprehensive comparison. The first functional unit was defined as one feddan per cultivation cycle, where geranium was assessed over a 6-month season and violet over a 12-month annual cycle (one feddan equals 4200 m²). The second functional unit was defined as 1 kg of essential oil for geranium or 1 kg of concrete for violet. The area-based functional unit enables comparison of land-use efficiency and ecosystem service provision, while the product-based functional unit facilitates comparison with international LCA studies of essential oil production12.

System boundaries

System boundaries were defined as cradle-to-gate with explicit inclusion of biogenic carbon flows, encompassing all processes from field preparation through product extraction. This system boundary definition differs from conventional MAP LCA studies in two critical respects. First, we explicitly quantify and credit photosynthetic CO2 uptake during the entire cultivation period, treating this uptake as a negative emission that offsets fossil carbon releases from process energy and inputs. This approach recognizes that MAP crops, as photosynthetic organisms, provide the ecosystem service of atmospheric CO2 removal during growth, and that this service has climate relevance when evaluated on the timescale of cultivation cycles25,26. Second, we quantify oxygen production as a co-benefit of photosynthesis, enabling assessment of life-support ecosystem services alongside carbon accounting. These inclusions transform the LCA from an emissions-only assessment to a net greenhouse gas balance evaluation, providing more comprehensive characterization of climate impact.

Specifically, the system included field operations such as land preparation, planting, irrigation with metered electricity consumption for pumping, and documented fertilizer application. The biomass growth phase encompassed photosynthetic CO2 uptake and O2 release during the entire cultivation period, calculated from measured biomass production using standard stoichiometric relationships and carbon content factors (see “Life cycle inventory”). Post-harvest handling included harvesting operations and short-distance transport to the on-farm processing facility (less than two kilometers). Extraction processes comprised steam distillation for geranium and solvent extraction for violet, including all associated energy inputs. Finally, residue management involved composting of spent biomass with quantification of associated CH4 and CO2 emissions. Several processes were excluded from the system boundaries in accordance with typical agricultural LCA practice and ISO 14,044 guidance. These exclusions comprised upstream manufacturing of capital equipment such as distillation units and irrigation systems (long-lived assets with impacts amortized over multi-decade lifespans), packaging materials for the final products, distribution beyond the farm gate, and end-of-life disposal12.

This system boundary definition enables comparison with conventional MAP LCA studies through two complementary metrics. First, we report gross emissions (excluding photosynthetic uptake) to facilitate direct comparison with published studies employing emissions-only boundaries. Second, we report net greenhouse gas balance (emissions minus photosynthetic uptake) as the primary climate impact indicator, representing the innovation of this study. The net balance metric answers the question: does this MAP production system function as a net source or sink of atmospheric CO2 when cultivation-phase sequestration is credited against value-chain emissions? This framing is particularly relevant for climate policy discussions, carbon market development, and identification of climate-smart crop systems where agricultural production delivers net atmospheric CO2 removal rather than net addition.

Table 1 Conventional vs. this study.
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Carbon sequestration accounting and temporal considerations

A critical consideration in this LCA is the temporal dimension of carbon sequestration. This study distinguishes between temporary carbon storage and long-term sequestration. For both MAP species, photosynthetic CO₂ uptake during the growing cycle is credited as a negative emission within our system boundary. However, the permanence of this sequestration varies substantially depending on biomass fate. For geranium, the harvested aerial biomass (leaves and stems) undergoes steam distillation, during which much of the stored carbon is released back to the atmosphere through combustion of fuel and volatilization during the extraction process. The essential oil itself represents a relatively small fraction of biomass carbon; the majority is re-emitted within weeks to months of harvest. Therefore, geranium’s carbon uptake represents primarily temporary storage rather than permanent atmospheric removal. For violet, the concrete product may retain carbon for several years depending on end-use application in perfumery and cosmetics, though eventual oxidation and biodegradation will release this carbon on decadal timescales. Our system boundary follows the cradle-to-gate approach, crediting photosynthetic uptake during cultivation while tracking process emissions through extraction. The reported negative carbon footprint for geranium thus represents the net flux during the cultivation-extraction cycle rather than permanent CO₂ removal from the atmosphere. This temporal framing is essential for proper interpretation—the climate benefit derives from the offset of process emissions by concurrent photosynthetic uptake, effectively reducing the net fossil carbon released per unit of product, rather than from long-term carbon storage in biomass or soil. This approach aligns with recent LCA frameworks for biogenic carbon accounting that distinguish between biogenic carbon temporarily cycled through agricultural systems and fossil carbon permanently transferred from geological reservoirs to the atmosphere.

Study sites and data collection

Primary data for geranium (Pelargonium graveolens) were collected from commercial plantations in Fayoum Governorate, Egypt, located at coordinates 29°18’N, 30°50’E at an elevation of approximately 26 m above sea level. Data collection occurred during the 2023 growing season spanning from March to August. Information aggregated from thirty-seven feddans of commercial production was normalized to a one-feddan basis to ensure representativeness while maintaining statistical reliability. Geranium was cultivated in rows with 50-cm spacing, achieving a plant density of approximately 20,000 plants per feddan. Flood irrigation was applied at intervals of ten to fourteen days depending on climatic conditions and soil moisture levels.

Data for violet (Viola odorata) were collected from a one-feddan intensive cultivation plot in Giza Governorate, positioned at coordinates 30°01’N, 31°12’E at an elevation of approximately 22 m. The complete 12-month production cycle was monitored throughout 2023. Violet was grown under partial shade conditions using drip irrigation systems to optimize water use efficiency.

The extraction processes employed distinct methodologies for each crop based on industry-standard practices. Geranium essential oil was extracted using steam distillation in a 500-liter capacity still operated with liquefied petroleum gas as the fuel source. Processing temperatures were maintained between 100 and 105 °C, with distillation duration of three to four hours per batch. Each batch processed 150 kg of fresh biomass, achieving an oil recovery rate of 0.54 g of oil per kilogram of fresh biomass. Violet concrete was obtained through solvent extraction using hexane in a Soxhlet apparatus. Fresh flowers were first dried to reduce moisture content from approximately 75 to 12%, then extracted at temperatures between 60 and 70 °C for 6–8 h. A solvent-to-biomass ratio of four-to-one (volume to weight) was employed, yielding 0.21% concrete on a dry weight basis. Hexane solvent recovery was assumed at 87% based on primary data from commercial processors, with makeup solvent accounting for 13% losses to volatilization and residual solvent in spent biomass. The emission factor for hexane (2.1 kg CO₂ -eq per kg) includes both production impacts (1.2 kg CO₂ -eq per kg) and combustion of unrecovered solvent (0.9 kg CO₂ -eq per kg). This recovery rate is consistent with published jasmine and violet extraction studies reporting solvent recovery efficiencies of 80 to 95% for batch solvent extraction systems.

Comprehensive inventory data were collected through multiple measurement methods. Irrigation electricity consumption was determined through direct metering of pump operations. Fertilizer quantities were documented from farm application records maintained for agronomic management purposes. Fuel consumption for distillation and extraction was measured volumetrically using calibrated containers. Biomass yields were determined through systematic weighing at harvest, while oil and concrete yields were quantified through volumetric and gravimetric measurements respectively. Residue quantities were calculated as the difference between input biomass and extracted product.

Life cycle inventory

The quantification of photosynthetic CO2 uptake and oxygen production follows established physiological relationships and stoichiometric principles, adapted from forest carbon accounting and agricultural carbon sequestration literature (IPCC, 2006; Lal, 2004). While direct measurement of net ecosystem exchange through eddy covariance or chamber-based techniques provides the most accurate site-specific fluxes, such approaches require specialized instrumentation and extended monitoring periods beyond the scope of most LCA studies. We therefore employ the biomass-based calculation method, which estimates CO2 uptake from measured biomass production using tissue carbon content and photosynthetic stoichiometry. This approach, widely accepted in agricultural greenhouse gas inventories and forest carbon accounting27, provides conservative estimates appropriate for comparative LCA applications where relative differences between systems are of primary interest. The method explicitly accounts for the fundamental photosynthetic reaction (6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2), ensuring mass balance consistency between CO2 consumed and O2 produced.

Oxygen production and CO₂ absorption

Photosynthetic oxygen production and carbon dioxide uptake were estimated using the fundamental stoichiometric relationship of photosynthesis, expressed as: 6CO₂ + 6 H₂O → C₆H₁₂O₆ + 6O₂. This relationship indicates that for every 264 g of CO₂ absorbed, 192 g of O₂ are produced, representing a molar ratio of 6:6 and a molecular weight ratio of 1.375:1.

Canopy photosynthetic capacity was estimated through a three-component approach. First, canopy coverage was determined through monthly field measurements using the grid intersection method, with five replicate one-square-meter quadrats measured per field following the methodology of Patrignani and Ochsner28. Second, net primary productivity was estimated from final biomass accumulation, including both above-ground biomass and estimated root biomass, incorporating tissue carbon content of 45% on a dry weight basis, which is typical for C3 photosynthetic pathway plants as documented in IPCC29 guidelines. Third, growing period integration involved calculating carbon fixation integrated over the full growing season while accounting for different canopy development stages from establishment through senescence.

Total carbon dioxide absorbed per feddan was calculated as the total biomass carbon content in kilograms divided by the atomic weight of carbon (12) and multiplied by the molecular weight of CO₂ (44). Total oxygen produced in cubic meters per feddan was then calculated as the CO₂ absorbed in kilograms divided by 1.375 (the mass ratio), further divided by 1.43 kg/m3 (the density of O₂ at standard temperature and pressure). This approach provides conservative estimates of gross photosynthetic fluxes during the cultivation period, consistent with agricultural carbon sequestration methodologies established in IPCC29.

Greenhouse gas emissions

Emission sources were quantified using IPCC29 Tier 1 emission factors combined with country-specific data where available. Irrigation electricity consumption for geranium was measured at 430 kilowatt-hours per feddan per season through direct metering, while violet utilized drip irrigation with minimal electricity requirements that were not separately quantified and were assumed negligible compared to extraction energy. The emission factor applied for grid electricity was 0.5 kg of CO₂-eq/kW-h, representing the Egyptian national grid average as reported by the Egyptian Electricity Holding Company30.

Fertilizer-related emissions were calculated based on documented NPK application rates for both crops. Emission factors for fertilizer production were applied as follows: 1.15 kg CO₂-eq/kg of nitrogen, 0.20 kg CO₂-eq/kg of P₂O₅, and 0.15 kg CO₂-eq/kg of K₂O, all sourced from29. Direct nitrous oxide emissions from soil application of synthetic fertilizers were calculated using an emission factor of 0.016 for wet-climate conditions as specified in the IPCC29 Refinement.

Fuel consumption for distillation and extraction represented a major emission source for both crops, though the magnitude differed substantially. For geranium, liquefied petroleum gas consumption was measured at 15 kg per 150-kg fresh biomass batch, with an applied emission factor of 3.00 kg CO₂-eq per kilogram of LPG from IPCC27. For violet, hexane solvent use was quantified at 120 L per feddan annually, with a comprehensive emission factor of 2.87 kg CO₂-eq per kg of hexane accounting for both production and combustion, sourced from the European Reference Life Cycle Database31.

Composting emissions from spent biomass were quantified assuming aerobic composting conditions. Methane emissions were calculated at 4 g CH₄ per kg of dry biomass, while nitrous oxide emissions were calculated at 0.6 g N₂O per kg of dry biomass, both based on IPCC29. These emissions were converted to CO₂-equivalents using global warming potential factors from IPCC’s Fifth Assessment Report with a 100-year time horizon: 28 for methane and 265 for nitrous oxide32.

For violet solvent extraction, hexane consumption was calculated accounting for solvent recovery and reuse. The assumed recovery rate of 87% reflects commercial batch extraction practice, where solvent is recovered through distillation after extraction. Makeup solvent requirements (13% of total throughput) account for losses to volatilization during heating, residual solvent in spent biomass that cannot be economically recovered, and minor spillage during handling. Per kilogram of violet concrete produced, total hexane throughput is approximately 15.2 kg, of which 13.2 kg is recovered and reused while 2.0 kg represents makeup solvent from external supply. The emission factor of 2.1 kg CO2 eq per kg hexane used in the inventory comprises: (1) production emissions for makeup solvent (1.2 kg CO2 eq per kg hexane produced, covering refinery operations and transport), and (2) combustion emissions from unrecovered hexane assumed to volatilize and oxidize in the atmosphere (0.9 kg CO2 eq per kg hexane based on stoichiometric combustion of C6H14). This emission factor approach is conservative, as some portion of volatilized hexane may persist in the atmosphere without immediate oxidation.

Net carbon footprint calculation

The net CO₂-eq footprint per feddan was calculated as the sum of all emission sources (fuel emissions, irrigation emissions, fertilizer emissions, and composting emissions) minus the photosynthetic CO₂ uptake during the growing period. Negative values indicate that the system functions as a net carbon sink where absorption exceeds emissions, while positive values indicate a net carbon source where emissions exceed absorption.

Carbon Use Efficiency (CUE) was defined as a dimensionless ratio of photosynthetic CO₂ absorption divided by direct process emissions. Values greater than one indicate that carbon absorption exceeds emissions, suggesting net carbon sequestration potential, while values less than one indicate that emissions exceed absorption, representing a net carbon source. This metric provides a normalized indicator of the carbon balance independent of scale.

Uncertainty and sensitivity analysis

Monte Carlo simulation with 10,000 iterations was conducted using Python version 3.10 with NumPy version 1.24 to propagate parameter uncertainty through the calculation framework. Input parameters were assigned probability distributions based on data quality and variability assessments. Emission factors were assigned normal distributions with ± 20% relative standard deviation to reflect uncertainty in published values and applicability to local conditions. Photosynthetic absorption estimates were assigned normal distributions with ±15% relative standard deviation to account for spatial and temporal variability in canopy photosynthesis. Yields and activity data were assigned normal distributions with ±10% relative standard deviation based on measurement precision and field variability.

From the Monte Carlo simulation results, probability distributions of net footprints were generated for both crops, and 95% confidence intervals were calculated using the percentile method. Sensitivity analysis was conducted to identify key drivers of net footprint variability through calculation of Spearman rank correlation coefficients between input parameters and output footprint values, enabling prioritization of data quality improvements and identification of critical intervention points.

Scenario analysis

For violet, which exhibited a positive carbon footprint under baseline conditions, mitigation scenarios were modeled to evaluate the potential for emission reductions through energy source substitution. Three alternative energy sources were evaluated assuming either partial (50%) or complete (100%) substitution of fossil fuel energy used in the hexane extraction process. The first scenario involved solar thermal energy using a Scheffler concentrator system with an assumed system efficiency of 30% based on recent field studies17. The second scenario assumed biogas-derived heat generated from on-farm residue anaerobic digestion with an assumed yield of 0.3 cubic meters of biogas per kilogram of volatile solids. The third scenario evaluated the impact of grid renewable energy penetration at 50%, representing an achievable near-term grid decarbonization target for Egypt. Emission reductions were calculated as proportional to the substitution fraction (50% or 100%) of baseline distillation and extraction energy requirements.

Statistical software

Data analysis, visualization, and Monte Carlo simulations were performed using Python version 3.10 with key libraries including pandas 2.0 for data manipulation, matplotlib 3.7 for visualization, scipy 1.11 for statistical functions, and numpy 1.24 for numerical computations. Descriptive statistics included means, standard deviations, and 95% confidence intervals calculated using appropriate parametric or non-parametric methods depending on distribution characteristics. Effect sizes for net footprint comparisons between crops were calculated using Cohen’s d statistic to quantify the magnitude of differences independent of sample size, with interpretation following standard conventions where d = 0.2 represents a small effect, d = 0.5 represents a medium effect, and d = 0.8 represents a large effect.

Results

Crop performance and yield characteristics

Field measurements revealed substantial differences in biomass production and product yields between the two MAP systems. Geranium cultivation over the 6-month growing season produced a total fresh biomass of 3700 kg per feddan, with essential oil yield of 20 kg per feddan, corresponding to an oil content of 0.54% on a fresh weight basis. Violet cultivation over the 12-month cycle yielded 150 kg of fresh flowers per feddan. Following drying and solvent extraction, violet produced 31.5 kg of concrete per feddan, representing a concrete yield of 0.21% on a dry flower weight basis. The lower absolute biomass production in violet reflects its specialized cultivation for flower production rather than whole-plant harvest, as well as the more intensive and selective harvesting regime required for this high-value product. The comprehensive summary metrics for both crops are presented in Table 2, which consolidates oxygen production, CO₂ absorption, net carbon footprint, oil yield, product carbon intensity, and Carbon Use Efficiency. This table enables direct quantitative comparison of the two systems across all key performance indicators. The stark contrast between geranium’s negative net footprint (– 375 kg CO₂ per feddan) and violet’s positive footprint (+ 15,972 kg CO₂ per feddan) is immediately apparent, as is the order-of-magnitude difference in product carbon intensity (– 18.75 versus + 507.04 kg CO₂ per kg product). The Carbon Use Efficiency values (1.09 for geranium versus 0.43 for violet) quantitatively confirm that geranium operates above the carbon-neutral threshold while violet operates substantially below it.

Table 2 Summary metrics by crop (per feddan).
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Oxygen production and carbon dioxide absorption

Photosynthetic gas exchange during the cultivation periods demonstrated the substantial ecosystem service potential of MAP cultivation. Geranium produced 54,324 cubic meters of oxygen per feddan during its 6-month growing season, corresponding to absorption of 155,632 kg of CO₂. These values reflect the rapid canopy development and sustained photosynthetic activity characteristic of geranium under Egyptian field conditions, with peak canopy coverage reaching approximately 85% of ground area by the third month. Violet generated 11,148 cubic meters of oxygen per feddan over its 12-month cycle, with corresponding CO₂ absorption of 12,700.8 kg. The lower per-area oxygen production in violet despite the longer growing period reflects its lower canopy density and partial-shade cultivation requirements, which limit photosynthetic capacity per unit land area.

Carbon footprint components

Detailed greenhouse gas accounting revealed markedly different emission profiles between the two crops, as presented comprehensively in Table 3. This table disaggregates the net carbon footprint into five component flows: fuel for distillation or extraction, irrigation electricity, fertilizer production, composting-related emissions, and photosynthetic absorption (shown as a negative value representing CO₂ removal from the atmosphere). The table structure clearly reveals the sources of the contrasting net balances, showing that while both crops have similar low-magnitude emissions from fertilizers and composting, they diverge dramatically in fuel consumption and moderately in irrigation requirements.

Table 3 Carbon footprint components and process parameters (per feddan).
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For geranium, total direct emissions summed to 4,140 kg CO₂-eq/feddan per season, distributed across four main sources. Fuel for steam distillation contributed 1,900 kg CO₂-Eq. (45.9% of total emissions), representing the single largest emission source. Irrigation electricity accounted for 1,800 kg CO₂-Eq. (43.5%), reflecting the substantial energy requirements of flood irrigation under Egyptian conditions. Fertilizer production contributed 80 kg CO₂-Eq. (1.9%), while composting of spent biomass released 360 kg CO₂-Eq. (8.7%) through methane and nitrous oxide emissions. The photosynthetic absorption of 4,515 kg CO₂ nearly balanced these emissions, leaving only a small net negative residual.

Violet exhibited a dramatically different emission structure, with total direct emissions of 27,999.65 kg CO₂-eq per feddan annually. Solvent extraction fuel dominated the emission profile at 27,247.50 kg CO₂-eq, representing 97.3% of total emissions (Fig. 1). This overwhelming contribution reflects both the energy-intensive nature of hexane extraction and the low product yield requiring processing of large quantities of biomass per unit output. Fertilizer production contributed 80 kg CO₂-Eq. (0.3%), while composting emissions totaled 672.15 kg CO₂-Eq. (2.4%). Irrigation electricity was not separately quantified for violet due to the minimal energy requirements of the drip irrigation system employed. Photosynthetic absorption of 12,028.80 kg CO₂ offset less than half of total emissions, resulting in the substantial positive net balance.

Fig. 1
Fig. 1The alternative text for this image may have been generated using AI.
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Pie chart showing the relative contribution of emission sources to violet total carbon footprint (excluding photosynthetic absorption). Solvent extraction fuel dominates at 97.3% of total emissions (27,248 kg CO2-eq/feddan), dwarfing contributions from fertilizer production (0.3%) and composting (2.4%). This extreme concentration identifies fuel-to-solvent heating as the critical intervention point for emissions reduction. Key Takeaway: Solvent extraction fuel represents the overwhelming hotspot (over 97%) in violet production.

The comparative emission-absorption dynamics are visualized in Fig. 2, which presents total emissions versus photosynthetic absorption for both crops. The stacked bar chart clearly illustrates that geranium’s total emissions (orange segment) are nearly balanced by its photosynthetic absorption (blue segment extending below zero), resulting in the slight net negative balance. In contrast, violet shows total emissions far exceeding photosynthetic absorption, with the large positive orange segment overwhelming the modest blue absorption segment. This visualization emphasizes the fundamental difference in carbon balance between the two systems, where geranium achieves near-equilibrium between emissions and sequestration while violet exhibits a substantial imbalance driven by extraction energy requirements.

Fig. 2
Fig. 2The alternative text for this image may have been generated using AI.
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Stacked bar chart comparing total process emissions (orange) and photosynthetic CO2 absorption (blue) for geranium and violet per feddan. Geranium achieves near-equilibrium with emissions (4050 kg CO2-eq) nearly balanced by absorption (4425 kg), resulting in a net carbon sink. Violet shows substantial imbalance, with emissions (28,672 kg CO2-eq) exceeding absorption (12,700 kg) by more than 2:1, resulting in a net carbon source of 15,972 kg CO2-eq / feddan per year. Key Takeaway: Geranium achieves carbon balance; violet shows 2:1 emission-to-absorption imbalance.

Net carbon footprint

When photosynthetic CO₂ absorption was credited against direct emissions, the two crops exhibited opposite carbon balance outcomes (Fig. 3). Geranium demonstrated a net negative carbon footprint of – 375 kg CO₂-eq/feddan per season. This net sink status resulted from photosynthetic uptake of 4515 kg CO₂ during the growing period, which exceeded the 4140 kg CO₂-eq in direct emissions by 375 kg. The Carbon Use Efficiency for geranium was 1.09, indicating that absorption exceeded emissions by 9%.

Fig. 3
Fig. 3The alternative text for this image may have been generated using AI.
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Bar chart showing net carbon footprint (emissions minus photosynthetic absorption) per feddan. Geranium demonstrates a negative footprint of – 375 kg CO2-eq / feddan per season, qualifying as a net carbon sink where photosynthetic uptake exceeds all process emissions. Violet exhibits a positive footprint of + 15,972 kg CO2-eq / feddan per year, functioning as a substantial carbon source. The 16,347 kg difference highlights the profound impact of extraction method (steam distillation vs. solvent extraction) on net climate performance. Key Takeaway: Geranium is a net carbon sink (– 375 kg); violet is a net carbon source (+ 15,972 kg).

In stark contrast, violet exhibited a net positive carbon footprint of 15,971.65 kg CO₂-eq / feddan annually. Despite absorbing 12,028.80 kg of CO₂ during its 12-month growing period, this uptake offset only 43% of the 27,999.65 kg CO₂-eq in total emissions. The resulting Carbon Use Efficiency of 0.43 indicates that emissions exceeded absorption by more than a factor of two, driven primarily by the energy-intensive solvent extraction process.

Product-based carbon intensity

When expressed per unit product, the carbon intensity differences became even more pronounced (Table 1). Geranium essential oil exhibited a carbon footprint of – 18.75 kg CO₂-eq per kilogram of oil, indicating that the land-based carbon sequestration more than offset all processing emissions when allocated to the oil product. This negative intensity suggests that geranium oil production provides a net climate benefit under current Egyptian cultivation and processing practices.

Violet concrete showed a carbon footprint intensity of 507.04 kg CO₂-eq per kilogram of concrete. This high carbon intensity reflects the combination of low product yield (31.5 kg/feddan) and high extraction energy requirements. Compared on a per-kilogram-product basis, violet’s carbon intensity exceeded geranium’s by a factor of 27, even before accounting for the opposite signs of their net balances.

Multi-criteria performance comparison

A comprehensive multi-criteria comparison of the two crops is presented in Fig. 4, which displays four normalized performance metrics on a radar chart: oxygen production potential, CO₂ absorption capacity, low footprint score (inverse of net emissions), and oil yield. The radar plot reveals geranium’s superior performance across most environmental metrics, with particularly strong scores for oxygen production (1.0, normalized to maximum) and CO₂ absorption (1.0), combined with a favorable low-footprint score (0.95) reflecting its near-carbon-neutral status. Oil yield scores moderately (0.40) due to relatively low per-area productivity. Violet’s radar profile shows more constrained performance, with lower scores for oxygen potential (0.20), CO₂ absorption (0.08), and particularly for low-footprint score (0.02), reflecting its substantial positive carbon balance. Violet’s oil yield metric (concrete production normalized to geranium oil) scores at 0.79, higher than geranium due to greater per-kilogram product value despite lower total biomass. This multi-criteria visualization underscores that geranium delivers superior ecosystem services while violet’s performance is constrained primarily by extraction-phase emissions rather than cultivation-phase productivity.

Fig. 4
Fig. 4The alternative text for this image may have been generated using AI.
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Radar chart comparing geranium and violet on four normalized sustainability metrics (0 to 1 scale): oxygen production potential, CO2 absorption capacity, low-footprint score (inverse of emissions), and oil yield per feddan. Geranium exhibits a balanced profile with strong environmental performance (oxygen: 1.0, CO2 absorption: 1.0, low footprint: 0.95) but moderate yield (0.40). Violet shows higher yield (0.79) but substantially weaker environmental scores (oxygen: 0.20, CO2 absorption: 0.08, low footprint: 0.02), demonstrating the trade-off between product value and climate impact under current extraction technologies. Key Takeaway: Geranium delivers superior ecosystem services; violet prioritizes yield over environmental performance.

Contextualization within global MAP production systems

To position the Egyptian geranium and violet systems within the broader landscape of aromatic crop environmental performance, Table 4 synthesizes reported environmental hotspots across representative MAP species from recent life cycle assessment literature published between 2018 and 2025. This comparative analysis reveals consistent patterns across diverse cropping systems and geographic contexts. For rose (Rosa damascena), multiple studies identify steam and hydrodistillation thermal energy as the dominant hotspot, with particularly high impacts reported in Bulgaria where low oil yields (0.02–0.03%) necessitate processing of enormous biomass quantities per unit output15. Lavender (Lavandula species) exhibits similar distillation energy hotspots, compounded by low-yield effects that amplify per-kilogram-product impacts14. Rosemary (Rosmarinus officinalis) LCA studies from Portugal document combined electricity and thermal energy burdens in distillation as the primary contributors to carbon footprint, with impact magnitudes strongly dependent on electricity grid carbon intensity12.

Table 4 Reported environmental hotspots across aromatic crops (2018–2025).
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Basil (Ocimum species) presents a somewhat different profile, with studies of greenhouse-cultivated edible basil identifying greenhouse electricity for climate control and water management as dominant factors, though these studies focus on fresh herb rather than essential oil production33. Jasmine (Jasminum species) parallels violet in its reliance on solvent extraction with hexane for absolute production, with multiple sources confirming that solvent production, handling, and associated energy represent the overwhelming environmental burden34,35. The consistent emergence of extraction energy as the primary hotspot across steam-distilled oils (rose, lavender, rosemary, geranium) and solvent extraction systems (jasmine, violet) underscores the critical importance of thermal energy decarbonization for MAP value chain sustainability. Table 3 documents the specific key references for each crop-process combination, providing a literature foundation for cross-system comparison and identification of generalizable intervention strategies.

Uncertainty analysis

Monte Carlo simulation with 10,000 iterations provided probabilistic characterization of the net carbon footprints (Figs. 5 and 6). For geranium, the distribution of net footprint values exhibited a mean of – 386 kg CO₂-eq per feddan with a 95% confidence interval ranging from – 2051 to + 1257 kg CO₂-eq. The probability that geranium operates as a net carbon sink (net footprint less than zero) was 67.4%, indicating that despite parameter uncertainty, the system more likely than not provides net carbon sequestration. The relatively wide confidence interval reflects the compounding uncertainties in both photosynthetic uptake estimates and emission factor applications.

Fig. 5
Fig. 5The alternative text for this image may have been generated using AI.
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Monte Carlo simulation (N = 10,000 iterations) showing probability distribution of geranium net carbon footprint accounting for parameter uncertainty. Mean: – 386 kg CO2-eq / feddan; 95% confidence interval: – 2051 to + 1257. The distribution shows 67.4% probability of net carbon sink status (negative values), indicating robust climate benefit despite parameter variability in photosynthetic uptake and emission factors. The wide confidence interval reflects compounded uncertainties but maintains majority probability of negative footprint. Key Takeaway: 67% probability that geranium functions as net carbon sink under parameter uncertainty.

Fig. 6
Fig. 6The alternative text for this image may have been generated using AI.
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Monte Carlo simulation (N = 10,000 iterations) showing probability distribution of violet net carbon footprint. Mean: 15,901 kg CO2-eq / feddan; 95% confidence interval: 4,671 to 27,175. The distribution remains entirely positive across virtually all simulated scenarios, with only 0.3% probability of carbon sink status, confirming with high confidence that violet functions as a net carbon source under current solvent extraction practices regardless of reasonable parameter variations. Key Takeaway: 99.7% probability that violet functions as net carbon source; finding is robust to uncertainty.

For violet, the net footprint distribution showed a mean of 15,901 kg CO₂-eq per feddan with a 95% confidence interval spanning from 4,671 to 27,175 kg CO₂-eq (Fig. 7). The probability that violet operates as a net carbon sink was only 0.3%, essentially confirming with high confidence that the current system functions as a net carbon source under all realistic parameter combinations. The distribution remained entirely positive across virtually the full range of simulated scenarios, demonstrating the robustness of this finding to parameter uncertainty.

Fig. 7
Fig. 7The alternative text for this image may have been generated using AI.
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Bar chart with 95% confidence interval error bars comparing net CO2 footprint between crops. Geranium: – 386 kg CO2-eq / feddan (95% CI: – 2051 to + 1257); Violet: 15,901 kg CO2-eq / feddan (95% CI: 4671 to 27,175). The non-overlapping confidence intervals indicate statistically significant difference (Cohen d = 3.97, very large effect size). Mean difference: 16,287 kg CO2-eq / feddan, equivalent to annual emissions from approximately 3.5 passenger vehicles. Key Takeaway: Crops differ by approximately 16 metric tons CO2 per feddan with high statistical confidence.

Statistical comparison of the two crops revealed a very large effect size with Cohen’s d equal to 3.97, indicating that the difference in net carbon footprints between violet and geranium is substantial and highly meaningful. The mean difference (violet minus geranium) was 16,287 kg CO₂-eq per feddan with a 95% bootstrap confidence interval ranging from 4809 to 27,665 kg CO₂-eq. This difference represents approximately 16 metric tons of CO₂-eq per feddan annually, equivalent to the annual emissions from approximately 3.5 passenger vehicles.

Product carbon intensity distributions

On a product intensity basis, Monte Carlo analysis yielded similar conclusions with even greater relative differences (Figs. 8 and 9). Geranium oil exhibited a mean net intensity of – 19.3 kg CO₂-eq per kilogram of oil with a 95% confidence interval from – 102.6 to + 62.9 kg CO₂-eq per kilogram. The wide confidence interval reflects the sensitivity of per-product allocation to yield variability, with lower oil yields resulting in less favorable (more positive) carbon intensity values. Violet concrete showed a mean intensity of 504.8 kg CO₂-eq per kilogram of concrete with a 95% confidence interval from 148.3 to 862.7 kg CO₂-eq per kilogram. The high baseline intensity combined with low yield variability resulted in a distribution that remained strongly positive across the uncertainty range.

Fig. 8
Fig. 8The alternative text for this image may have been generated using AI.
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Monte Carlo simulation (N = 10,000) of geranium oil carbon intensity (kg CO2-eq per kg oil). Mean: – 19.3 kg CO2-eq per kg oil; 95% CI: – 102.6 to + 62.9. The negative mean intensity indicates that on average, geranium oil production sequesters more CO2 than it emits when photosynthetic uptake is allocated to the oil product. The wide distribution reflects sensitivity to oil yield variability, with lower yields producing less favorable (more positive) intensities. Key Takeaway: Geranium oil exhibits negative mean carbon intensity (– 19.3 kg CO2-eq per kg oil).

Fig. 9
Fig. 9The alternative text for this image may have been generated using AI.
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Monte Carlo simulation (N = 10,000) of violet concrete carbon intensity (kg CO2 -eq per kg concrete). Mean: 504.8 kg CO2 -eq per kg concrete; 95% CI: 148.3 to 862.7. The consistently high positive intensity reflects the combination of energy-intensive solvent extraction and low product yield (31.5 kg per feddan). The distribution remains entirely positive, indicating that violet concrete production is a net carbon source across all realistic parameter ranges under current practices. Key Takeaway: Violet concrete shows high carbon intensity (505 kg CO2 -eq per kg) with no negative scenarios.

Global benchmarking of MAP performance

To contextualize the Egyptian case studies within broader MAP cultivation systems, a qualitative global comparison was conducted across six widely cultivated aromatic crops: geranium, violet, rose, lavender, basil, and jasmine (Fig. 10). Performance metrics were normalized on a zero-to-one scale based on literature-reported ranges for oxygen production potential, CO₂ absorption capacity, low-footprint score (inverse of typical production emissions), and oil yield. The radar visualization reveals distinct performance profiles for each species. Geranium exhibits the most balanced profile with strong scores across all metrics (O₂ potential 0.90, CO₂ absorption 0.95, low footprint 0.85, oil yield 0.45), confirming its position as a relatively climate-smart crop. Violet shows moderate O₂ and CO₂ performance (0.50 and 0.45 respectively) but poor footprint scores (0.10) due to extraction intensity, with moderate yield (0.65). Rose demonstrates intermediate performance across metrics (0.60–0.70 range), reflecting moderate productivity with steam distillation processing. Jasmine exhibits a profile similar to violet with good yield (0.75) but constrained environmental performance (O₂ 0.45, footprint 0.15) due to solvent extraction requirements. This cross-species comparison highlights that extraction method (steam versus solvent) emerges as a critical determinant of net environmental performance, often outweighing differences in cultivation-phase productivity.

Fig. 10
Fig. 10The alternative text for this image may have been generated using AI.
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Qualitative radar comparison of six medicinal and aromatic plant species (geranium, violet, rose, lavender, basil, jasmine) on four normalized metrics: oxygen production potential, CO2 absorption capacity, low-footprint score, and oil yield. Data synthesized from literature (2018 to 2025). Geranium exhibits the most balanced profile (strong environmental metrics, moderate yield). Extraction method emerges as key determinant: steam-distilled oils (rose, lavender, geranium) show better environmental profiles than solvent-extracted absolutes (jasmine, violet), despite comparable cultivation-phase productivity. Key Takeaway: Extraction method (steam vs. solvent) is the primary driver of environmental performance differences.

Scenario analysis for emission mitigation

Given violet’s substantial positive carbon footprint driven by extraction energy, scenario analysis evaluated the potential for emission reductions through renewable energy substitution (Table 5; Fig. 11). Under the baseline scenario with conventional hexane extraction using fossil fuel energy, the net footprint was 15,972 kg CO₂-eq / feddan annually as previously reported. Substituting 50% of distillation fuel with solar thermal energy reduced the net footprint to 2,348 kg CO₂-eq / feddan, representing an 85% reduction. Complete (100%) solar thermal substitution resulted in a net footprint of – 11,276 kg CO₂-eq / feddan, transforming violet from a strong net source to a significant net sink.

Table 5 Scenario outcomes for violet net CO₂ (kg/feddan/year).
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Fig. 11
Fig. 11The alternative text for this image may have been generated using AI.
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Bar chart showing violet net CO2 footprint under six decarbonization scenarios: baseline fossil fuel (15,972 kg CO2-eq per feddan), 50% solar thermal (2348 kg), 100% solar thermal (– 11,276 kg), 50% biogas (2348 kg), 100% biogas (– 11,276 kg), and 50% grid renewable electricity (2348 kg). Complete renewable energy substitution transforms violet from substantial carbon source to significant carbon sink, demonstrating 171% emission reduction. Scenario modeling confirms that extraction energy source, not cultivation practices, determines violet climate impact. Key Takeaway: 100% renewable extraction energy converts violet from carbon source to carbon sink (– 11,276 kg).

Biogas substitution scenarios yielded identical results to solar thermal scenarios at equivalent substitution levels, since both alternatives were modeled as zero-emission energy sources relative to the baseline fossil fuel. 50% biogas substitution achieved the same 2348 kg CO₂-eq per feddan as solar thermal at 50%, while 100% biogas substitution similarly achieved – 11,276 kg CO₂-eq per feddan. The grid renewable energy scenario at 50% renewable penetration also resulted in 2348 kg CO₂-eq per feddan, equivalent to the 50% substitution scenarios, reflecting the proportional nature of emission reductions to energy source decarbonization.

These scenarios demonstrate that the carbon balance of violet production is highly sensitive to extraction energy source, and that technically feasible renewable energy interventions could shift the system from a substantial net carbon source to a modest net carbon sink. The magnitude of potential emission reductions (approximately 27 metric tons CO₂-eq per feddan through complete renewable substitution) represents a significant climate mitigation opportunity for the violet value chain in Egypt.

Discussion

Interpretation of carbon balance outcomes

The contrasting carbon footprints of geranium and violet illuminate the critical role of post-harvest processing technology in determining the net climate impact of medicinal and aromatic plant value chains. Geranium’s achievement of carbon neutrality, and indeed a modest net sink status of − 375 kg CO₂-eq per feddan per season, demonstrates that MAP cultivation can deliver simultaneous economic and environmental benefits when extraction processes are energy-efficient relative to photosynthetic uptake. The near-perfect balance between geranium’s emissions (4140 kg CO₂-eq) and absorption (4515 kg CO₂) reflects the fortunate convergence of several favorable factors: relatively high oil content requiring less biomass processing per unit product, moderate energy requirements for steam distillation compared to solvent extraction, and robust photosynthetic capacity during the 6-month growing period. This finding positions geranium among the rare agricultural systems that approach carbon neutrality when cultivation-phase sequestration is credited against full value-chain emissions.

Violet’s positive footprint of 15,972 kg CO₂-eq per feddan annually, by contrast, exemplifies how extraction intensity can overwhelm cultivation-phase carbon benefits. The dominance of solvent extraction fuel, contributing 97.3% of total emissions, creates an emissions profile fundamentally different from steam-distilled crops. This pattern reflects the thermodynamic reality that solvent extraction, despite avoiding steam generation, requires substantial energy for solvent production, heating, evaporation, and recovery. The low concrete yield of 0.21% dry weight necessitates processing approximately 476 kg of dried flowers per kilogram of concrete, amplifying the per-product energy intensity. While violet’s 12-month growing cycle enables 12,700 kg of CO₂ absorption, this uptake offsets only 43% of extraction-phase emissions, leaving a large positive residual. These findings align with recent LCA studies of jasmine absolute production, which similarly identify hexane extraction as the dominant environmental hotspot34.

Comparison with global essential oil LCA literature

The Egyptian geranium results accord well with the international LCA evidence base for steam-distilled essential oils, while extending the literature by explicitly quantifying photosynthetic uptake. Recent Portuguese studies of rosemary essential oil reported carbon footprints of 8.8 to 19.3 kg CO₂-eq per kilogram of aromatic extract, depending on feedstock moisture and extraction method, with hydrodistillation accounting for 60 to 85% of total impacts12. Our geranium finding of − 18.75 kg CO₂-eq per kilogram oil falls below this range specifically because the Portuguese studies employed cradle-to-gate boundaries excluding photosynthetic uptake, while our approach credits in-season sequestration. When Egyptian geranium emissions are calculated exclusive of uptake (4,140 kg CO₂-eq ÷ 20 kg oil = 207 kg CO₂-eq/kg oil), the value exceeds Portuguese rosemary due to Egypt’s higher grid carbon intensity (0.5 kg CO₂/kWh versus Portugal’s approximately 0.3 kg CO₂/kWh) and flood irrigation energy requirements. This comparison underscores both the importance of system boundary definition in LCA interpretation and the substantial influence of country-specific electricity grids on agricultural carbon footprints.

For lavender in Colombia, González-Aguirre and colleagues (2020) similarly identified distillation energy as the primary hotspot, with low oil yields (0.5–0.8%) amplifying per-kilogram impacts. Bulgarian rose oil production exhibits even more extreme energy intensity due to yields as low as 0.02%, requiring distillation of 5000 kg of petals per kilogram of oil15. Against this global context, Egyptian geranium’s 0.54% oil content represents a moderate yield that keeps per-product energy requirements within manageable bounds. The consistency of distillation energy as the dominant hotspot across geranium, rosemary, lavender, and rose reinforces the generalizability of thermal energy decarbonization as a priority intervention for steam-distilled essential oil value chains globally.

Our violet findings parallel recent jasmine absolute LCA results, where solvent extraction similarly dominates the carbon footprint. Industry reports from the International Fragrance Association confirm that hexane production and recovery account for 70–90% of jasmine absolute environmental impacts35. The challenge for solvent-extracted products lies in the difficulty of renewable energy substitution, as hexane itself is a petroleum derivative whose production emissions are embedded before reaching the extraction facility. While solar thermal can replace heating energy, the hexane molecule’s embodied carbon remains unavoidable without bio-based solvent alternatives. Emerging research on supercritical CO2 extraction offers potential for complete elimination of hexane use and associated emissions. Studies report CO2 extraction can achieve comparable or superior yields to hexane extraction while eliminating solvent production and recovery emissions entirely, though capital costs remain substantially higher than conventional hexane systems (). If renewable electricity powers the CO2 compression, such systems could reduce solvent-related emissions by 90 + percent compared to current hexane extraction practice. Emerging research on deep eutectic solvents and supercritical CO₂ extraction suggests potential pathways to reduce solvent-related impacts, though these technologies remain predominantly at laboratory scale for most MAP applications34.

Probabilistic assessment and uncertainty implications

The Monte Carlo uncertainty analysis provides critical probabilistic context for interpreting the carbon balance findings. For geranium, the 67.4% probability of net carbon sink status indicates moderate confidence in the climate benefit, with roughly one-third of simulated scenarios producing net positive (source) footprints under parameter combinations at the unfavorable extremes of input distributions. This probability reflects the compounding uncertainties in three primary domains: (1) photosynthetic uptake estimation, where biomass-to-carbon conversion factors and tissue carbon content vary with cultivar, nutrient status, and environmental conditions; (2) emission factor applications, particularly for grid electricity which varies temporally and has changed substantially as Egypt integrates renewable capacity; and (3) operational parameters such as fuel consumption rates and irrigation scheduling, which differ across farms and seasons. The 95% confidence interval spanning from – 2051 to + 1257 kg CO2 eq per feddan quantifies this variability, indicating that while the central tendency favors carbon neutrality, the outcome is sensitive to system-specific conditions.

This probabilistic framing contrasts sharply with deterministic LCA studies that report point estimates without explicit uncertainty characterization. Recent meta-analyses of agricultural LCA studies indicate that fewer than 15% incorporate formal uncertainty analysis despite widespread recognition that parameter variability substantially influences conclusions36. The sensitivity of geranium carbon balance to parameter uncertainty underscores the importance of site-specific primary data collection and conservative parameter selection when claims of carbon neutrality or sequestration are advanced. For policy and market applications requiring high confidence in carbon accounting, the 67% probability suggests that geranium would qualify for carbon credit certification under conservative additionality criteria but might not meet more stringent standards requiring 90 + percent probability of net benefit.

Violet exhibits contrasting uncertainty characteristics. The 99.7% probability of net carbon source status, with virtually the entire probability distribution remaining positive, indicates robust findings that persist across all reasonable parameter variations. Even at the favorable extreme of the 95% confidence interval (4671 kg CO2 eq per feddan), violet remains a substantial net emitter, suggesting that parameter uncertainty does not materially affect the qualitative conclusion. This robustness reflects the overwhelming dominance of a single, well-characterized emission source (hexane extraction fuel at 97.3% of total emissions), which exhibits relatively low uncertainty compared to more distributed emission profiles. The narrow coefficient of variation for solvent extraction fuel consumption, based on industrial process norms, limits the scope for favorable parameter combinations that could shift violet to carbon neutrality under current practices.

The scenario analysis results demonstrate that technological interventions can fundamentally alter these probabilistic outcomes. Complete solar thermal substitution for violet extraction energy shifts the mean footprint from + 15,901 to – 11,276 kg CO2 eq per feddan, a swing of 27,177 kg representing 171% emission reduction relative to baseline. Under this scenario, the probability of carbon sink status would approach 99 + percent (inverse of the baseline), transforming violet from a robust carbon source to a robust carbon sink. This finding carries important policy implications: while current violet production unambiguously contributes to net emissions, the system is not inherently climate-incompatible but rather critically dependent on energy source. The sensitivity to energy substitution scenarios indicates that supply chain decarbonization pathways exist and are technically feasible, though economic viability depends on solar thermal capital costs, financing availability, and potential carbon price incentives.

Comparison with uncertainty analyses in related MAP LCA literature reveals both methodological consistency and knowledge gaps. Moura et al.12 employed Monte Carlo simulation for rosemary essential oil in Portugal, reporting similarly wide confidence intervals driven primarily by yield variability and distillation efficiency uncertainty. Their finding that extraction energy uncertainty dominated overall footprint variability parallels our violet results. However, few published MAP LCAs explicitly model photosynthetic uptake uncertainty, limiting comparative assessment of net carbon balance probability distributions. The convergence of our findings with established LCA uncertainty analysis frameworks36, regarding the relative importance of foreground data quality versus background database uncertainty suggests that investment in site-specific measurement of key operational parameters (fuel consumption, irrigation electricity, actual yields) provides greater value for reducing decision uncertainty than refinement of generic emission factors.

Technology adoption pathways for renewable energy integration in MAP processing exhibit distinct feasibility profiles. Solar thermal distillation, demonstrated at pilot scale in India17 and Egypt37, offers direct fossil fuel displacement with payback periods of 18–24 months under favorable financing conditions. The technical maturity of Scheffler concentrators and parabolic trough systems reduces technology risk, though operational challenges including thermal storage for cloudy periods and system maintenance in agricultural settings remain implementation barriers. Biogas from agricultural residues presents an alternative pathway particularly suited to integrated farm systems where multiple feedstocks (MAP residues, animal manure, crop stubble) enable year-round digester operation. Egypt Strategic Development Plan 2030 targets 20% renewable energy in agriculture by 2030, creating policy alignment for MAP sector investments. Financial mechanisms including blended finance (combining climate fund grants with commercial credit), processor-backed equipment financing recovered through product purchase agreements, and renewable energy cooperatives pooling infrastructure investments across multiple producers offer implementation models that address smallholder capital constraints.

Ecosystem services and multi-functionality of MAP systems

Beyond carbon footprint, MAP cultivation provides substantial oxygen production co-benefits. Geranium generated 54,324 cubic meters of oxygen per feddan per season while violet produced 11,148 cubic meters annually, representing meaningful contributions to atmospheric oxygen budgets. Given human respiratory consumption of approximately 200 cubic meters annually per person, one feddan of geranium provides oxygen sufficient for 272 person-years during its 6-month season, while violet supports 56 person-years over 12 months. MAP multi-functionality extends to biodiversity support, pollinator habitat provision, and soil organic matter accumulation through residue composting. Aromatic plants cultivated with reduced pesticide inputs can serve as refugia for beneficial insects within intensive agricultural landscapes22, supporting broader agroecological frameworks that emphasize ecological intensification3.

Practical decarbonization pathways

Beyond extraction energy, irrigation management offers additional mitigation opportunities. Geranium flood irrigation electricity consumption of 1800 kg CO2-eq per season could be reduced 30–50% through drip irrigation conversion, with further gains from solar photovoltaic pumping. Combined solar distillation and irrigation would eliminate approximately 3700 kg CO2-eq of geranium total emissions (90%), deepening the net sink to approximately – 4000 kg CO2-eq per feddan and creating potential for verified carbon credit generation. Fertilizer management through precision application, soil testing, and slow-release formulations can reduce nitrogen rates 15–30% while maintaining yields29. For violet, where fertilizer represents only 0.3% of emissions, such interventions offer marginal footprint benefits but deliver important soil health co-benefits.

Policy and market implications

The demonstrated climate-smart potential of Egyptian geranium, and the improvability of violet through renewable energy integration, carry implications for agricultural policy and essential oil market development. Egypt’s Sustainable Agricultural Development Strategy 2030 emphasizes crop diversification, water use efficiency, and renewable energy adoption as core pillars. MAPs align with all three priorities: they diversify traditional cereal-dominated rotations, deliver high economic value per unit water in water-scarce regions, and present suitable applications for distributed solar thermal technologies. Policy support mechanisms could include preferential credit for solar extraction equipment, technical assistance programs for renewable energy integration, and premium pricing mechanisms for certified low-carbon essential oils in export markets.

International fragrance and cosmetics industries increasingly adopt corporate sustainability commitments that include Scope 3 supply chain emissions reduction targets. Major industry players including L’Oréal, Estée Lauder, and Symrise have announced carbon neutrality goals for 2025 to 2030, creating demand for low-carbon essential oil sourcing38,39,40. Egyptian producers who can document negative or near-zero carbon footprints through third-party verification may access price premiums, preferential contracts, and market differentiation opportunities. The development of product-specific carbon footprint methodologies for essential oils, aligned with ISO 14,067 and the Greenhouse Gas Protocol Product Standard, would facilitate credible carbon claims and create market pull for decarbonization investments.

At the smallholder level, where much Egyptian MAP production occurs, adoption of capital-intensive renewable energy technologies faces financial and technical barriers. Business models involving processor-financed equipment with cost recovery through product purchase agreements, renewable energy cooperatives that share solar infrastructure across multiple producers, and blended finance mechanisms combining public grants with commercial credit could overcome these barriers. Development programs supported by international climate finance (Green Climate Fund, Global Environment Facility) could catalyze initial investments while building demonstration effects that drive broader adoption. The favorable economic returns of MAPs relative to traditional crops provide ability to service equipment loans that would be infeasible for lower-margin commodities.

Limitations and methodological considerations

Several limitations warrant acknowledgment. First, the photosynthetic uptake estimates, while based on established biomass-to-carbon conversion factors and stoichiometric relationships, represent approximations of dynamic seasonal processes. Direct eddy covariance flux measurements or chamber-based net ecosystem exchange quantification would provide more precise uptake estimates and capture temporal dynamics including nighttime respiration, though such measurements were beyond the scope and resources of this study. The assumption of 45% tissue carbon content, while standard for C3 plants, may not precisely reflect MAP-specific values that could vary with nutrient status and environmental conditions.

Second, the study employed single-season data from specific sites, limiting representation of inter-annual and spatial variability. Multi-year observations across diverse agroecological zones would strengthen the generalizability of findings and enable assessment of climate variability impacts on both yields and carbon balances. The geranium data, while aggregated from thirty-seven feddans providing reasonable replication, represent a single production year that may not capture yield extremes associated with drought, pest outbreaks, or other stresses. The violet data from a single one-feddan plot, while intensively monitored, similarly lack spatial and temporal replication.

Third, system boundaries excluded several potentially relevant processes. Upstream manufacturing of capital equipment (distillation stills, irrigation systems), while excluded per LCA convention for long-lived assets, does entail embodied carbon that would be relevant for comprehensive footprinting if amortized over equipment lifespans. Transport and distribution beyond the farm gate, also excluded, can contribute substantially to product carbon footprints when essential oils are exported globally, though these impacts are largely external to producer control. Allocation of multi-functional impacts between essential oils and co-products (spent biomass, hydrosols) was simplified by treating composting as the baseline residue fate; alternative allocation approaches (economic allocation, system expansion) could yield different quantitative outcomes while preserving qualitative conclusions about extraction energy dominance.

Fourth, the scenario analysis of renewable energy substitution employed simplified assumptions about system efficiency and emission displacement. Actual solar thermal system performance varies with weather, maintenance, and operational factors not captured in the constant 30% efficiency assumption. Biogas yield from residue digestion depends on feedstock composition, digester design, and operating conditions that introduce uncertainty into the modeled emission reductions. Grid renewable energy scenarios assumed proportional emission reductions without accounting for temporal mismatch between renewable generation and extraction energy demand, which could be relevant for intermittent solar photovoltaic electricity versus baseload extraction operations.

Future research directions

Priority research needs include longitudinal field studies of MAP carbon balances across multiple growing seasons and diverse agroecological zones within Egypt, capturing variability in yields, input requirements, and environmental outcomes. Such studies would strengthen the evidence base for policy decisions and enable development of region-specific management recommendations. Comparative assessments of additional MAP species cultivated in Egypt, including basil, jasmine, chamomile, and fennel, would expand the climate-smart crop portfolio and identify optimization opportunities across the sector.

Detailed techno-economic analysis of renewable energy integration options, incorporating capital costs, operating costs, financing structures, and sensitivity to input price volatility, would inform investment decisions and policy design. Pilot demonstrations of solar extraction systems at commercial scale, with rigorous monitoring of energy performance, oil quality, and economic returns, would reduce perceived technology risks and build capacity for broader adoption. Comparative evaluation of emerging extraction technologies, including supercritical CO₂, microwave-assisted extraction, and bio-based solvents, could identify alternatives that deliver both improved environmental performance and maintained product quality.

Integration of MAP carbon balance findings into broader landscape-scale carbon accounting frameworks would enable evaluation of crop diversification strategies at farm and regional scales. Whole-farm carbon footprint modeling that incorporates rotational dynamics, residue flows between crops, and shared infrastructure utilization could reveal synergies and tradeoffs not apparent in single-crop assessments. Finally, social research examining farmer perceptions, adoption constraints, and institutional support needs for climate-smart MAP intensification would complement biophysical research and inform implementation pathways that are both technically sound and socially feasible.

Conclusion

This study demonstrates that medicinal and aromatic plants can function as climate-smart crops when agronomic productivity is coupled with low-carbon processing pathways, though outcomes vary substantially across species and extraction methods. Under Egyptian field conditions, geranium (Pelargonium graveolens) achieved carbon neutrality with a modest net sink status of − 375 kg CO₂-eq per feddan per 6-month season, driven by photosynthetic uptake of 155,632 kg CO₂ that exceeded all value-chain emissions. This performance positions geranium among the rare agricultural systems delivering simultaneous economic returns and net carbon sequestration when cultivation-phase services are fully accounted. In contrast, violet (Viola odorata) exhibited a positive footprint of 15,972 kg CO₂-eq per feddan annually, reflecting the dominance of solvent extraction energy that overwhelmed the 12,700 kg CO₂ absorbed during the 12-month growing cycle.

The contrasting outcomes illuminate extraction technology as the critical determinant of MAP environmental performance. For geranium, steam distillation fuel and irrigation electricity contributed approximately equally to emissions (1900 and 1800 kg CO₂-eq respectively), while fertilizers and composting represented minor sources. For violet, hexane extraction accounted for 97.3% of total emissions, dwarfing all cultivation-phase inputs. This pattern aligns with international LCA evidence from rose, lavender, jasmine, and rosemary systems, where post-harvest thermal energy consistently emerges as the primary environmental hotspot. The generalizability of this finding across diverse MAP taxa and geographic contexts underscores thermal energy decarbonization as the highest-priority intervention for sector-wide sustainability improvement.

Scenario modeling demonstrates that renewable energy integration offers a technically and economically viable pathway to transform high-footprint systems. Complete substitution of violet’s extraction fuel with solar thermal energy would shift the net footprint from + 15,972 to − 11,276 kg CO₂-eq per feddan, representing a 170% swing from substantial source to significant sink. Egypt’s solar resource endowment of 5 to 7 kilowatt-hours per square meter daily, combined with proven Scheffler concentrator technologies achieving 27–33% efficiency in pilot studies, positions the country favorably for solar extraction adoption. Economic analyses from India report benefit-cost ratios of 1.5–1.8 and payback periods of 18–24 months for solar distillation systems, confirming financial viability alongside environmental benefits.

Beyond carbon mitigation, MAP cultivation delivers substantial ecosystem services including oxygen production (54,324 m³/feddan for geranium; 11,148 m³/feddan for violet), biodiversity habitat provision, and pollinator support. These multi-functional benefits strengthen the case for MAP integration into diversified farming systems, particularly in water-scarce regions where high economic value per unit water application enhances livelihood resilience. The climate-smart potential of MAPs aligns with Egypt’s Sustainable Agricultural Development Strategy 2030 priorities of crop diversification, water efficiency, and renewable energy adoption.

Practical recommendations for Egyptian MAP value chains include: (1) prioritization of solar thermal and biogas-derived heat for essential oil extraction, with policy support through preferential credit, technical assistance programs, and infrastructure co-investment; (2) conversion from flood to drip irrigation coupled with solar photovoltaic pumping to eliminate irrigation-related emissions; (3) precision nutrient management and legume integration to reduce synthetic fertilizer dependence; (4) valorization of spent biomass through controlled composting or anaerobic digestion with biogas capture; and (5) development of carbon footprint verification systems aligned with ISO 14,067 to enable market differentiation and premium pricing for low-carbon essential oils in international fragrance and cosmetics markets.

Future research priorities include: longitudinal multi-year studies across diverse agroecological zones to quantify yield and carbon balance variability; expansion to additional Egyptian MAP species including basil, jasmine, chamomile, and fennel; detailed techno-economic analysis of renewable energy options incorporating capital costs, financing structures, and risk factors; pilot demonstrations of solar extraction at commercial scale with rigorous performance monitoring; comparative evaluation of emerging technologies including supercritical CO₂ and bio-based solvents; landscape-scale carbon accounting integrating crop rotations and shared infrastructure; and social research examining farmer adoption constraints and institutional support needs.

This study provides quantitative evidence that Egyptian medicinal and aromatic plant production can transition from conventional energy-intensive systems to climate-positive value chains through strategic renewable energy integration and sustainable management practices. Geranium’s demonstrated carbon neutrality under current practices, and violet’s potential for transformation through solar substitution, illustrate that climate mitigation and agricultural development objectives need not conflict but can be mutually reinforcing when system design prioritizes both productivity and environmental integrity. As global essential oil markets increasingly demand verified sustainability credentials, Egyptian producers who lead in decarbonization stand to capture both environmental and economic advantages in a rapidly evolving competitive landscape.