ANAEROBIC DIGESTION

CONVERTING BIOWASTE INTO ENERGY

Anaerobic digestion is a biological process of degradation of organic matter by the action of bacteria and in the absence of oxygen.

The temperature and pH (neutral) conditions must be controlled throughout the anaerobic digestion process.

This degradation will produce, on the one hand, biogas rich in methane and, on the other hand, a stable and mineralised product, the digestate, which can be used as a natural fertiliser.

THERE ARE MANY SOURCES OF ORGANIC MATERIAL

BioRenGaz is developing a technology adapted to biowaste in Strasbourg. Biowaste is organic waste from natural plant or animal resources:

COMMUNITIES / RESTAURANTS / SUPERMARKETS / CITIZENS

Food biowaste, table waste

FOOD INDUSTRY

Brewery, distillery, cheese factory, sugar factory, etc.

AGRICULTURAL

Livestock waste, Slurry

WATER TREATMENT

WWTP sludge, paper mill

Anaerobic digestion offers us the possibility of recovering organic waste that would otherwise be completely wasted or thrown away in conventional dosmetic waste, to produce a green and renewable energy source, biogas.

This sector provides farms with an autonomy in fertiliser, ecological and odourless, while reducing the use of chemical fertilisers.

The energy produced can be used on site or sold to energy distributors in the form of electricity or gas, which considerably increases the annual income of the farmers or communities.

BIOGAS

Biogas is produced by the fermentation of organic waste of plant and/or animal origin in the digester. It is composed mainly of methane (CH4), carbon dioxide (CO2), water vapour, traces of sulphurous gases (H2S) and other minority compounds which vary according to the type of substrate being methanised.

There are several ways of recovering biogas:

• Heat and electricity production using a cogeneration engine, or only the production of heat with a biogas boiler. The heat produced is generally used on site for heating digesters and premises, and for hygienising biowaste.

• Biomethane production by purifying biogas to a methane content of over 95% and then compressing it for injection into the natural gas network.

• Biomethane fuel or CNG production. Currently, several ranges of vehicles can run on CNG (Compressed natural gas), a more ecological alternative to fossil fuels (diesel, petrol), with a very significant reduction in the particles emitted (-50 to -90% of NOx).

DIGESTATE

Digestate is the side product of organic matter anaerobic digestion. It is composed of mineral fertilising elements such as nitrogen, phosphorus and potassium, and trace elements. Water is also conserved during the anaerobic digestion process.

Its agronomic value is twofold, fertilising value (nutrient contribution for plants) and amending value (nutrient contribution for the soil), which represents a strong potential for agriculture.

Despite its virtues, digestate is currently considered as waste and must be recovered either by spreading the product on agricultural land, or by composting, or by mixing products.

However, the new European regulation No 2019/1009, "laying down rules for making EU fertilisers available on the market", will allow digestate to be included in this classification as well as its direct marketing. This regulation will be implemented in 2022.