Small-scale anaerobic digestion

A small-scale biogas reactor or anaerobic digester is an anaerobic treatment technology that produces (a) a digested slurry (digestate) that can be used as a fertilizer and (b) biogas that can be used for energy. Biogas is a mix ofmethane, carbon dioxide and other trace gases which can be converted to heat, electricity or light. Small-scale biogas reactors are typically designed to produce biogas at the household or community level in rural areas. The airtight reactors are filled with animal manure from the farm. Kitchen and garden wastes can also be added and toilets can directly be linked to thereactor for co-treatment of excreta.

In	Out
Blackwater, Faecal Sludge, Brownwater,Faeces, Excreta, Organic Solid Waste	Biogas, Sludge, Compost/Biosolids

Schematic of a biogas reactor. Source: TILLEY et al. (2014)

A biogas reactor is an airtight chamber that facilitates the anaerobic degradation ofblackwater, sludge, and/or biodegradable waste (e.g. animal manure, kitchen and garden wastes). It also facilitates the collection of the biogas, a mixture of methane (CH₄) and carbon dioxide (CO₂) produced in the fermentation processes in the reactor. The gas forms in the slurry and collects at the top of the chamber, mixing the slurry as it rises.The pressure exerted by the rising gas can be used to transport the gas to the collection vessel or directly to where it is going to be used. The digestate is rich in organics and nutrients, almost odourless andpathogens are partly inactivated.

The produced gas can be recovered and used either directly for cooking and lighting or it can be transformed into heat in a gas heater system or into combined heat and power (CHP) in acogeneration unit (MES et al. 2003; JENSSEN et al. 2004; WRAPAI 2009).

http://www.sswm.info/category/implementation-tools/wastewater-treatment/hardware/site-storage-and-treatments/anaerobic-di