Researchers at the Council of Scientific & Industrial Research - Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad are working on a set of integrated technologies that could solve two of the major challenges the world is facing today -- food wastage and energy deficit. The researchers discuss how biorefinery -- a facility that integrates biogenic waste conversion processes and technologies to produce fuels, power, heat and value-added chemicals -- can be a sustainable strategy for bioeconomy.
Food waste refers to the decrease of food in subsequent stages of food supply chain that may be caused accidentally or intentionally, ultimately leading to the generation of unwanted organic waste material. A report states that one third of the food produced for our needs, amounting to around 1.3 billion tons a year is wasted globally. Food waste is just not food wasted, but a lot more; land, water, energy and inputs -- all go to the bin along with the food. When the United Nations declared food waste as a global problem, it was reported that almost 8% of the greenhouse gas emissions comes from food waste.
The other major source of greenhouse gas (GHG) emissions are fossil fuels, which are increasingly becoming unsustainable sources of energy with the world being ‘energy hungry’ more than ever. The current methods of energy production do not match the rate of consumption, and reducing GHG emissions with the advent of ‘green’ fuels are the need of the day.
In the review study published in the journal Bioresource Technology, led by Dr. S. Venkata Mohan, Principal Scientist at CSIR - IICT, provides an overview of present and futuristic technologies available to generate ‘green’ energy, and other chemicals from food and related biogenic waste products, in turn, escalating the bio-economy.
Food waste predominantly constitutes organic compounds like carbohydrates, proteins and lipids (fats), which can be broken down to simpler compounds and then can be converted into a range of products by biological or bio-chemical reactions. Acidogenic fermentation or acidogenesis, for example, leads to the breakdown of organic compounds and conversion of these compounds into volatile fatty acids namely formic acid, acetic acid, propionic acid, butyric acid, iso-butyric acid and valeric acid in a cascade of biological reactions. Along with these acids, carbon dioxide and bio-hydrogen are also generated. Anaerobic digestion leads to conversion of these acids into bio-methane. Further optimizing the amount of bio-hydrogen and bio-methane produces bio-hythane. These acids are itself commodity chemicals and precursors for several other chemicals.
“The calorific value -- the amount of energy produced by the complete combustion of a fuel -- of diesel is 45.5 Mega joule (MJ) /Kg and that of the bio-hydrogen is 141.80 KJ/Kg. On the other hand, one kilogram of diesel burnt under ideal conditions will produce 2.65 Kg of CO2 and 1 Kg of petrol burnt under ideal conditions will produce 2.3 kg of CO2. However, bio-hydrogen when burnt will not emit CO2, making it an ideal green fuel”, says Dr. Mohan, talking about the greener aspect of bio-hydrogen.
Biodiesel is gaining rapid interest towards replacing petroleum diesel to some extent. Biodiesel faces a disadvantage of oxidative stability due to which when the bio-fuel is not processed and stored properly oxidation happens. Hence, researchers are now working around this challenge. “Biodiesel used in automobiles is generally employed in mixtures from B5 to B20 (diesel with 5 and 20% vol. of biodiesel, respectively) depending on the location. Further, to improve biodiesel oxidative stability, antioxidants are added. Additionally, utilizing microalgae as feedstock for biodiesel production can address several disadvantages of plant based biodiesel to some extent. Microalgae can generate as much as 40 times more oil per acre than bio-oil producing plants and the oxidation stability of micro algal biodiesel is more than plant based biodiesel, which means that it can be stored for a longer period of time when compared to plant based biodiesel”, says Dr. Mohan.
The researchers also list ‘electro fermentation’ -- a process where electrodes are used to electrochemically control microbial fermentation -- as another promising method to convert organic sources into valuable chemicals and biofuels. “Electrode placement in a microbial environment creates a potential, influencing the rate of reaction by regulating the electron flow, thereby enhancing resource recovery from the bioprocesses”, explains Dr. Mohan. Bio-ethanol and biobutanol, common products obtained from the biochemical synthesis of solvents, could serve as alternative source of fuel in the near future.
Food waste also acts as an abundant source of electrons for Electroactive Bacteria (EAB) -- a class of bacteria that are capable of transferring electrons outside the cells to an electrode or metal ore -- thus acting as a source of ‘bioelectricity’. Scientists have also developed similar technologies to generate bio-fertilizers and bio-polymers, that provide ‘greener’ alternatives to what we currently use.
The future holds a lot of promise to bioeconomy. According to a report published by BCC Research, the global market for biorefinery technologies will grow from $466.6 billion in 2016 to $714.6 billion by 2021, with a compound annual growth rate of 8.9% for the period of 2016-2021. Of course, from citizens building basic biorefineries at home to the policy makers and the government playing a major role in making this happen, a lot needs to be done to realise these revenues.
“Steps must be taken for realizing the potential opportunities that exist with waste mining and biorefineries. Government can support biorefineries through soft loans or land allotments. The government's support for producing a long-term plan for a bioeconomy with incentive structure, policy and ameliorating market distortions will support bioeconomy”, says Dr. Mohan.
Biorefineries indeed promise a revolutionising clean and green future we all look forward to. Who knows, the food that you throw today may charge up your phone tomorrow or, run your car!
This article is based on a research paper titled “Food Waste Biorefinery: Sustainable Strategy for Circular Bioeconomy” published in Bioresource Technology Journal. Financial support was given through funding from CSIR in the form of Network Project and Department of Biotechnology (DBT) as research grant.