There’s a high potential for food waste to turn into energy and it’s being recognized all around the world. But why do countries still avoid taking actions and waste over 70% of the world’s food by sending it right into landfills? According to the United Nations Food and Agriculture Organization, about one third of the world’s food – nearly 1.3 billion tonnes- are lost or wasted. Food waste can cost the world’s developed nations about $680 billion a year. Composting and digestion of food waste can be both wasteful and time-consuming. But what are the consequences of continuing to make use of food waste? Well, there are two ways to solve the food waste problem and turn it into environmentally friendly biofuel, with the use of simple chemical processes – anaerobic digestion and hydrothermal liquefaction.
Anaerobic digestion of organic waste (a.k.a. biomass) produces Biogas, which can then be burned to generate electricity or heat. Biogas is a renewable energy source that is generated by natural processes. Food waste is stored in digestion tanks, where microorganisms break it down in an environment where it’s oxygen-free. The microorganisms will emit methane gas or Biogas during the decomposition process.
This treatment is accomplished through a series of biological processes in which microorganisms decompose biomass or waste feedstocks in the absence of oxygen. Anaerobic digestion, including hydrothermal liquefaction, produces biogases, which can be burned to generate electricity and heat or converted into clean natural gas and transportation.
Animal manure, food waste, and other organics available are often used as biogas feedstocks. Throughout the entire process, numerous pumps are used to transfer semi-solids and slurries. These pumps are also protected by using in-line two shafted grinders. These grinders can remove solids that have accumulated at the bottom of the digestion tanks or that entered through the feedstock. In certain anaerobic digestion systems, drum screens are used to filter out the beneficial microorganisms that are flushed from the digester. These will be processed and used in the anaerobic digestion process to handle additional waste.
Hydrothermal liquefaction is the process of heating food waste under high pressure, effectively pressure-cooking it, in order to produce an oil that can be converted into fuel. Once converted, the watery food waste that remains after liquefaction is then subjected to anaerobic digestion. The converted gas can be used to generate electricity and heat.
The benefits of hydrothermal liquefaction over other methods for biomass processing are significantly high. However, since high pressures are required for processing, special reactor and separator designs are needed, and full-scale plants require large capital investments, this is why this technology is not commonly used up till’ today. To improve the consistency of the products and yields, this reaction uses homogeneous or heterogeneous catalysts. The carbon and hydrogen in organic materials like biomass or peat are thermochemically converted into hydrophobic compounds with low viscosity but high solubility. Heavy engines can utilize the petrol, or it can be converted to transportation fuels like diesel, gasoline, or jet fuel.
Process of Hydrothermal Liquefaction
- Long carbon chain molecules found in biomass are thermally cracked and oxygen is extracted in the form of water (H20) and carbon dioxide (CO2), leading to the development of high hydrogen to carbon ratio bio-oil.
- Temperatures of 250 °C to 550 °C, with pressures of 5-25 MPa, and catalyst are used in the process for 20-60 minutes. Temperatures may be raised or lowered to increase gas or liquid yields. Water in the biomass becomes either subcritical or supercritical at these temperatures and pressures, acting as a reactant, solvent, and catalyst.
Other methods of directly extracting methane from landfills exist, but combining anaerobic digestion and hydrothermal liquefaction to treat food waste is a more effective way to do so. Plus, the liquefaction stage generates an additional resource from the wasted food.
Breweries, dairy farms, coffee shops, and slaughterhouses produce enough organic waste to power hundreds of average homes each day. Of course, somewhere to gather, sort, and process this waste is needed. The world is experiencing unprecedented population growth, rapid urbanization, increase of affluence, and a scarcity of energy resources. Both governments and people would have to promote waste diversion in order for this to succeed. People are encouraged to distinguish their organic and food waste in places where Waste to Energy (WTE) systems are used. This way, everyone can save money on rubbish bills and provide a continual source of material to make WTE systems work.
Food waste, whether during its production phase or after being placed in the market, reduces the amount of food available for consumption. Food prices are determined by supply and demand, just like every other commodity. Since food demand is ever continuous, any decrease in supply would cause prices to rise, putting the poorest of us at risk. Food waste is a serious problem that has ramifications for food security, natural resource use, and climate change. However, by making incremental improvements in our buying habits and everyday lives, we can all positively contribute to its reduction. To reduce the amount of food waste we send to landfills each year, we as consumers must work together to avoid waste in the first place. When waste cannot be prevented, we must recycle food waste into goods or energy sources that support society, such as compost, animal feed or biogas itself.