Novel mutant camelina and jatropha as valuable feedstocks for biodiesel production

The global demand for alternative energy sources is driven by climate change concerns, rising energy consumption, energy security issues, and the need for efficient resource utilization. Biodiesel, a renewable fuel substitute for petroleum diesel, offers a solution. It is chemically composed of fatty acid methyl esters, obtained via transesterification of vegetable oils with alcohol. Biodiesel burns cleaner than petroleum diesel, producing fewer pollutants. Research focuses on identifying cost-effective and sustainable biodiesel feedstocks, including edible and non-edible oils, algal oils, and genetically engineered plant oils. Jatropha, while a high-oil-yielding plant, presents drawbacks including toxicity and environmental concerns. Camelina, with its short growing season, low harvesting costs, and high oil content, is gaining interest as an alternative. However, limited research exists on mutant camelina lines for biodiesel production. This study aimed to compare biodiesel production from jatropha and novel mutant camelina lines, evaluating the latter's suitability as a superior feedstock for biodiesel production.

Previous studies have highlighted the potential of various feedstocks for biodiesel production, including microalgae and genetically engineered plants. Jatropha has been recognized for its potential for large-scale biodiesel production; however, concerns about its toxicity and negative environmental impacts have been raised. Camelina sativa, while possessing desirable characteristics for biodiesel production, has been criticized in previous studies for exhibiting poor oxidative stability, high distillation temperature, and a high potential for coke formation during combustion—factors attributed to the high percentage of polyunsaturated fatty acids in its oil. These previous studies provided the rationale for investigating novel mutant lines of camelina to potentially overcome these limitations. A study in Thailand showed Camelina to have a higher net energy ratio than Jatropha for biofuel production. Camelina seeds also contain high levels of oil, protein, and lipids, with a variable fatty acid composition depending on genotype and environmental conditions. The unsaturated fatty acids in Camelina oil are beneficial for cardiovascular health.

Three thousand camelina mutant lines (M5 progenies) were obtained from the University of California, Davis, and sown to produce M6 progenies. Fifty high-yielding and drought-tolerant lines were selected. Oil was extracted from these lines using a cold press method. Jatropha oil was obtained from a local market. Biodiesel was produced via transesterification using both acid (H2SO4) and base (KOH) catalyzed reactions. Different catalyst concentrations were tested to optimize biodiesel yield. The fatty acid composition of the biodiesel was determined using GC-FID. Fuel properties, including pH, density, viscosity, free fatty acids (FFA), acid value, saponification value, iodine value, and cetane number, were determined using standard methods. Specific gravity was determined using a standard specific gravity bottle. Iodine value (IV) was calculated using a standard formula involving titration with Na2S2O3.5H2O. Saponification value (SV) was determined through titration with 0.5N HCl after saponification. Acid value was measured by titration with 0.1N NaOH. Cetane number (CN) was calculated using a formula incorporating IV and SV.

The optimized biodiesel yield was 96.28% for mutant camelina and 92.8% for jatropha, achieved using 0.125% KOH as a catalyst. GC-FID analysis showed that mutant camelina biodiesel contained primarily oleic acid (46.54 wt%), followed by linolenic acid (20.41 wt%) and linoleic acid (16.55 wt%). Jatropha biodiesel primarily consisted of oleic acid (45.03 wt%), linoleic acid (25.07 wt%), and palmitic acid (19.31 wt%). Mutant camelina biodiesel exhibited a pH of 6.82 ± 0.08 at 0.125% KOH, while jatropha biodiesel had a pH of 7.30 ± 0.03. The density of mutant camelina biodiesel ranged from 0.74 to 0.89 g/ml, mostly within the European standard range (0.86–0.90 g/ml), while jatropha biodiesel density was lower (0.67–0.72 g/ml). Viscosity for mutant camelina biodiesel was 113–119 cP, compared to 64–82 cP for jatropha biodiesel. Mutant camelina biodiesel showed lower FFA (0.35–0.43%), acid value (0.59–0.85), and saponification value (120.87–149.35) compared to jatropha biodiesel (FFA: 10.56–12.98%; acid value: 21–23.55; saponification value: 177.39–198.9). Mutant camelina biodiesel had a higher iodine value (130.2–157.9) than jatropha biodiesel (109.7–123.1), indicating higher unsaturation. Finally, mutant camelina biodiesel exhibited a higher cetane number (48.53–59.35) than jatropha biodiesel (47.76–51.26), meeting both European and American standards.

The results demonstrate that mutant camelina oil is a superior feedstock for biodiesel production compared to jatropha oil. The higher biodiesel yield, superior fuel properties (particularly the cetane number), and lower FFA content of mutant camelina biodiesel address the shortcomings identified in previous studies on non-mutant camelina. The improved fuel properties likely result from the altered fatty acid composition of the mutant lines, specifically the higher oleic acid content. The findings support the commercialization of mutant camelina for biodiesel production, offering a sustainable and environmentally friendly alternative to petroleum diesel. The lower viscosity of the mutant camelina biodiesel is also advantageous for engine performance.

This study successfully demonstrated the potential of novel mutant camelina lines as a promising feedstock for biodiesel production. Mutant camelina biodiesel exhibited superior fuel properties compared to jatropha biodiesel, meeting or exceeding international standards. Future research could focus on optimizing cultivation practices for mutant camelina, further enhancing its oil yield and fatty acid profile, and conducting comprehensive engine performance tests using the biodiesel produced from these mutant lines.

The study was conducted using a limited number of selected mutant camelina lines. Further research with a larger sample size and diverse environmental conditions is needed to confirm the generalizability of the findings. The study focused on laboratory-scale biodiesel production; larger-scale production processes might require further optimization. Long-term stability studies of the mutant camelina biodiesel under various storage conditions would also be beneficial.