The potential of Food waste as biomass for energy

Rising temperatures, melting glaciers, forest fires and devastating storms. To my belief, there is finally a consensus in developed countries to realize the threats of global warming. We know what happens, but what we should do to stop it is not so obvious. It is likely that fossil fuels for energy will slowly be phased out and replaced by options considered cleaner. Whether the replacement is nuclear, solar, hydro, wind power, energy from biomass or a mixture of these is uncertain; what I think will determine the outcome is mainly the economic viability of these options and how well they can compete with fossil energy sources.

I am certain that bioenergy belongs to the future and that the supply and demand will continue to increase. However, it is not so sure if bioenergy will be able to directly compete with fossil energy and other renewables in the long run. The bulk of the future transport sector in leaning more towards battery and fuel cell vehicles than biofuel powered options. Blending levels of biofuels in fossil based fuel might also not increase as much as expected if oil prices drop, as was observed as the covid-19 crisis lowered the global energy demand by 3.8% in Q1 2020 (1). Bioenergy for electricity shows promise but how clean is it really compared to renewables such and solar and wind?

What I believe is that biomass for energy will not compete with, but will serve as a complement to other energy sources. I think mainly we should focus on biomass which serve more purposes than generating energy, or biomass which is used in applications where no better options exist. This brings me to the intended topic of this blog post: second generation biomass and more specifically food waste, which is an example of the class of biomass which I think holds most potential based on the technology available today.

About one third of all food produced globally is being wasted, amounting to 1.3 billion tonnes of food in 2017 (2). Food waste is thus an abundant resource which offers great potential as an energy source. What I really like about food waste is that it serves yet another purpose. Apart from converting biomass into a refined energy source, it is part of a sustainable solution to the problems related to waste disposal. Food waste contains biomolecules such as proteins, carbohydrates and lipids and can for example be used as a substrate in anaerobic fermentation by microbes into a variety of refined products such as hydrogen, ethanol, and methane (3)(Figure 1).






Figure 1. Schematic figure of the substrates, intermediates, products, and type of bacteria involved in the process of anaerobic fermentation (3).

I think food waste is a very good example of a biomass which serves multiple purposes (both waste disposal and energy source) and can be utilized in applications where options are limited. This is because by anaerobic fermentation, food waste can be refined into for example methane, the main component of biogas (3). Biogas is not likely to be a realistic competitor for fossil fuels or electricity to power our private vehicles, but it serves as a good complement as a fuel for heavy transportation. Obviously fossil fuels are not preferable, todays batteries do not have the capacity to power heavy vehicles and other liquid biofuels are struggling with compatibility in combustion engines (4). Biogas can be considered a sustainable and economically viable option as fuel for heavy-duty vehicles such as buses (5). When liquified, biogas can also be considered as a marine fuel (6). As the shipping sector is a large contributor to greenhouse emissions and air pollution, I think this sector is very important for alternatives such as biofuels to take over.

It is worth to mention that I don’t think that producing biogas from food waste will save the planet. The problem is obviously much bigger, and efforts should mainly be concentrated to stop the overconsumption of food products in developed countries and to the reduce large amount of waste generated in the food-production and distribution chain.

References

1.          Renewables – Global Energy Review 2020 – Analysis – IEA [Internet]. [cited 2020 Sep 20]. Available from: https://www.iea.org/reports/global-energy-review-2020/renewables#abstract

2.          Paritosh K, Kushwaha SK, Yadav M, Pareek N, Chawade A, Vivekanand V. Food Waste to Energy: An Overview of Sustainable Approaches for Food Waste Management and Nutrient Recycling. Vol. 2017, BioMed Research International. Hindawi Limited; 2017.

3.          Dahiya S, Kumar AN, Shanthi Sravan J, Chatterjee S, Sarkar O, Mohan SV. Food waste biorefinery: Sustainable strategy for circular bioeconomy. Vol. 248, Bioresource Technology. Elsevier Ltd; 2018. p. 2–12.

4.          Motorists face huge repairs bill as Government biofuels destroy engines | Daily Mail Online [Internet]. [cited 2020 Sep 20]. Available from: https://www.dailymail.co.uk/news/article-564154/Motorists-face-huge-repairs-Government-biofuels-destroy-engines.html

5.          Cong RG, Caro D, Thomsen M. Is it beneficial to use biogas in the Danish transport sector? – An environmental-economic analysis. J Clean Prod. 2017 Nov 1;165:1025–35.

6.          Brynolf S, Fridell E, Andersson K. Environmental assessment of marine fuels: Liquefied natural gas, liquefied biogas, methanol and bio-methanol. J Clean Prod. 2014 Jul 1;74:86–95.