Producing Biofuels from Waste Coffee and Alcohol Products

by Reginald Davey (AZO Materials) Research into utilizing waste products has benefited several industries in recent years, improving their sustainability. Writing in the journal Energies, a team of scientists from Armenia and Poland has investigated the use of waste coffee and alcohol products to produce biofuels.

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Biogas and biohydrogen have been developed to help meet net zero carbon emission targets. Biohydrogen only emits water vapor after combustion and has a 3.5x higher energy content than oil.

Biogas is composed of methane and carbon dioxide, and is cleaner than conventional hydrocarbons such as coal, although it is not completely pollution-free. This sustainable fuel is composed of methane and carbon dioxide, with some nitrogen, ammonia, hydrogen, water vapor, and hydrogen sulfide.

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The alcoholic and non-alcoholic beverages industries are major contributors to worldwide waste. In distilleries, for example, 88% of raw materials become waste, making them a major polluter. Global spirits consumption is predicted to exceed thirty-eight billion liters by 2025. In the beer industry, 38.6 x 10⁶ tons of brewer’s spent grain is produced annually.

Non-alcoholic beverages such as tea and coffee generate vast quantities of waste materials. By-products of the beverages industry include coffee grounds, sugarcane bagasse, rice straw, wheat straw, brewer’s spent grain, and sorghum leaves. Many studies have already reported the use of these waste materials in biofuel and industrial chemical synthesis.

Amongst the various proposed methods for biofuel production, anaerobic digestion and dark fermentation have shown noteworthy promise. However, currently, technical challenges exist with using these techniques for the conversion of waste biomass into valuable alternative fuels. Treatment technologies have been explored in recent years, including physical, chemical, thermal, and hydrothermal treatments.

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The new paper in Energies has considered the use of anaerobic digestion for converting alcohol waste and spent coffee grounds into biohydrogen and biogas. The authors have explored preparation methods and pretreatments, along with gas analysis and the use of reagents.

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Sewage sludge from wastewater was used as the microbial inoculum in batch cultures. The authors note that there are several variables that must be accounted for, such as varying composition and concentration of microbial communities which occur seasonally or daily. Volatile and total solids in samples were determined prior to digestion using oven drying.

Study Results and Conclusions

The authors demonstrated that alcohol waste and spent coffee grains are promising high-organic content substrates. Utilizing these waste products could improve the efficiency and cost-effectiveness of biofuel production in the future. Untreated waste yielded enhanced methane and biogas production, whereas pre-treated waste yielded higher amounts of biohydrogen.

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For biohydrogen production, results indicated that spent coffee grains are more suitable, with data suggesting that the fermentation of alcohol waste, either treated or untreated, is not efficient for the production of this biofuel.

Biohydrogen yield obtained from spent coffee grounds is comparatively higher than using cotton waste but inferior to some other types of lignocellulosic waste. Results indicated a correlation between increased lignin removal and soluble sugar.

The authors concluded that acid hydrolysis treatment is beneficial for biohydrogen synthesis, whereas it is not important for biogas synthesis. Overall, the study has demonstrated the benefits of using spent coffee grounds and alcohol waste for the production of different biofuels and the effects of treatment technologies. The paper is valuable for future research in the field of sustainable biofuel production. READ MORE

Vanyan, L, Cenian, A & Trchounian, K (2022) Biogas and Biohydrogen Production Using Spent Coffee Grounds and Alcohol Production Waste Energies 15(16) 5935 [online] mdpi.com. Available at: https://www.mdpi.com/1996-1073/15/16/5935

Coffee and alcohol waste can be used as biofuels, say scientists (The Drinks Business)

From skincare to shampoo: World’s first coffee biorefinery creates new uses for upcycled coffee grounds (Beverage Daily)