Instead of being sent to landfill or flushed down the sink, coffee grounds can be recycled to produce biogas energy, compost and soil conditioners.
When coffee grounds and other food wastes are sent to landfill, they decompose to produce methane, a greenhouse gas with more than 20 times the global warming capacity of carbon dioxide. It's also a loss of an intensive source of nutrients and energy, as well as a potential source of hazardous pathogens and organic leachates that can contaminate surface and ground water.
If coffee grounds and other food wastes are recycled, however, valuable organic matter and nutrients can be recaptured for use as soil fertilisers, conditioners and mulch, and methane can be captured for electricity generation.
Food waste recycling collection for businesses is provided by a number of commercial operators and local councils. Generally, operators that accept food waste will accept coffee grounds, but check with your local operator.
Small businesses that have a worm farm or composting bin on the premises may be able to compost their own coffee grounds. Many local councils and community groups provide information and run workshops on worm farming and composting. Coffee grounds are natural fertilizers for acidic plants and can even repel plant pests. When mixed with soil, coffee grounds release a compound that helps balance the nitrogen in composts.
Some cafes and restaurants are able to give their coffee grounds away to customers who see coffee grounds as a valuable additive to their own compost heaps.
Hotels, restaurants and other large food service establishments may consider installing an industrial/commercial on-site composter to handle their food waste, including coffee grounds. For more information, visit the Recycled Organics Unit website.
For information on buying and using recycled organic products, or for more detailed information on composting, visit Compost for Soils.
The most common method of composting food waste in Australia is aerobic windrow composting (also called hot composting). In this process, food waste is mixed with other organic waste like wood chips or paper to before the material is formed into ‘windrows’ or mounded rows. The windrows are regularly turned and managed to optimise aerobic breakdown of the organic material (microbial breakdown of organic material in the presence of oxygen).
Another popular process that uses aerobic decomposition is in-vessel composting. This is similar to windrow composting, but the conditions can be more carefully controlled and the process is accelerated.
Biogas, including methane, is produced from anaerobic decomposition of organic waste (microbial breakdown of organic waste in the absence of oxygen). There are around 60 biogas generation facilities in Australia, producing biogas for electricity generation.
The solid material that is produced from composting is used as compost, mulch, potting mix, soil fertilisers and other soil conditioners. The liquid material that is produced from in-vessel composting and anaerobic decomposition is also used in soil conditioners, including liquid fertiliser that can be injected into the soil.
Compost Australia - a national program designed to build and spread knowledge about the production, benefits and use of recycled organics (compost). Created by Compost Australia.
Recycled Organics Unit (The University of NSW)