Recycling paper, glass, metal and plastics has become second-nature in most of the world. Now, it’s time to move to the next level—transforming food, water and animal waste into energy.
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Food waste, cooking oil and water waste are all significant environmental issues that can be turned into energy sources. By repurposing these waste products, we can reduce our reliance on non-renewable energy sources and reduce our carbon footprint. Biogas and biodiesel, two energy sources being made from the waste streams of homes, businesses and restaurants, as well as agriculture and forestry operations, are already economically viable replacements for some traditional natural gas and diesel fuels. In addition to being environmentally friendly, an advantage of expanding our biofuel capability is that we certainly don’t lack for raw material.
Food waste is a major issue in many countries, with an estimated one-third of all food produced worldwide going to waste. Instead of throwing this food away, it can be used to produce biogas through a process called anaerobic digestion. In anaerobic digestion, bacteria break down organic matter in the absence of oxygen, producing biogas as a byproduct. Biogas is approximately 60–80% methane with the remainder carbon dioxide. It can be readily combusted for cooking or heating. By cleaning the biogas and removing the carbon dioxide, it can be used as a direct replacement for natural gas for electricity, pipeline injection and natural gas-powered vehicles.
Water waste is another untapped resource that can be harnessed for energy. In many cities, wastewater treatment plants use anaerobic digestion to break down organic matter in sewage and produce biogas. These treatment plants can then use biogas generated from their own sludge to power their operations. Additionally, some homes and buildings have started to use "greywater" systems that recycle water from sinks and showers for irrigation or toilet flushing.
Diverting waste streams to anaerobic digestion plants can help extend the life of landfills. But landfills themselves, which are filled with food scraps, yard trimmings, junk wood, wastepaper and other carbon-based material, are also a source of waste that can be turned into energy. Anyone who has driven by a landfill knows it produces methane gas. Large waste management companies are now introducing processes to capture this naturally occurring biogas and convert it to usable energy. The technology to manage landfill biogas is relatively simple. Dispersed, perforated tubes are sent down into a landfill’s depths to collect gas, which is piped to a central collection area where it can be compressed and purified for use as fuel in generators or garbage trucks, or mixed into a natural gas supply.
The waste-to-energy process is well past the basic research stage. For example, in Sweden, more than half of the gas-powered vehicles are fueled by biogas. The goal, which seems reachable, is to have 100% of gas-driven cars using biogas by 2030.
Cooking oil is another common waste product that can be repurposed for energy. Used cooking oil can be processed into biodiesel, a renewable fuel source that can be used in standard diesel engines without requiring retrofitting. Biodiesel produces fewer carbon emissions than traditional diesel fuel, making it a more environmentally friendly option. However, it is not suitable for vehicles operating in more northern climates because it tends to coagulate at lower temperatures.
In 2019, the Dallas-Ft. Worth airport partnered with an outside company to collect used cooking oil from on-site restaurants and convert it into low-emission renewable fuels, such as sustainable aviation fuel and renewable diesel. Used oil from the restaurants’ fryers is collected, treated and upcycled into renewable fuels that are supplied to airlines across the country. Other countries have also initiated cooking-oil-to-energy programs. For example, in 2021 alone, McDonald’s in the Netherlands processed nearly 1,000 tons of used cooking oil into renewable biodiesel oil, which was used to truck products back to the fast-food restaurant sites.
Overall, repurposing food waste, cooking oil and water waste for energy is a smart and sustainable solution to our energy needs. By reducing waste and harnessing the energy potential of these resources, we can move towards a more sustainable and renewable future.
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