There are a number of treatment routes, other than landfill or MBT, for organic waste:
- Open air windrow composting: a method by which organic waste is laid down in long rows (windrows) and turned to allow it to break down aerobically. This process is only suitable for waste which does not contain animal by-products.
- In-vessel composting: a method by which organic waste is treated in enclosed vessels which are generally made of metal or concrete and allow for air flow and temperature to be controlled. This process is suitable for waste containing animal by-products.
- Anaerobic digestion: The method by which organic waste breaks down in the absence of oxygen to produce digestate and biogas, which can used to generate energy.
The end product from open windrow and IVC treatment – compost – can be used in horticulture, agriculture, land remediation and on brownfield sites. The output from anaerobic digestion (AD), which is known as digestate, can also be used in several of these applications.
Composters who treat food waste which includes animal-derived products, must comply with Animal By-Product Regulations (ABPR) to ensure the safety of the compost they make. The ABPR sets out a number of rules which composters must follow in order to kill any animal pathogens which could remain in the compost and potentially spread disease.
In Scotland, AD operators have reported a significant increase in the amount of food waste treatment taking place since the end of 2013, which could see an impact on the food waste price market in Scotland. This coincides with the Zero Waste Regulations coming to force from January 2014, which require Scottish businesses in urban areas producing more than 50kg of food waste to present it separately for collection.
letsrecycle.com provides four prices to indicate trends in the cost of UK composting and anaerobic digestion.
Prior to August 2012 three gate fee prices were shown: green waste disposal; food waste disposal; and, a selling price for compost.
Due to the growth of the anaerobic digestion market, the first two prices were replaced with prices for sending green waste for open windrow composting; sending food and/or green waste to in vessel composting; and, sending food waste to anaerobic digestion.