A chemical or natural product, added to the soil to fertilize it.

Context / Objectives

After the anaerobic digestion process, biogas is obtained on the one hand and digestate on the other.

The objective is to enable agronomic and/or energy recovery of effluents and organic waste.

Thus the digestate would provide interesting fertilizing elements for the soil. It can therefore be used as green manure.
This sector meets the needs of waste treatment, allowing both fertilization of plants and feeding of soil bacteria with organic matter.

Scientific explanations

Properties of digestate :
- Higher pH (basic)
- Rate of nitrogen mineralized in NH4+ form
- C/N ratio is lower
- Dry matter content is lower
Composition of digestate :
N, P, K, and trace elements are found as fertilizers.

Advantage/Disadvantage Tables


1- Phase separation treatment :
By centrifugation
With a screw press
This makes it possible to isolate on the one hand a solid fraction concentrated in organic matter and phosphate elements, which can be used as a basic amendment.
Then on the other hand a liquid fraction is concentrated in nitrogen, mainly in ammoniacal form, and in potassium.

2- Characterization of the digestate to be spread :
- Forecast quantities
- Production rate
- Agronomical value

3- Description of soil characteristics :
- Dry matter (%)
- Organic matter (in %)
- pH; overall nitrogen
- Ammoniacal nitrogen (as NH4)
- C/N ratio
- Exchangeable phosphorus (as P2O5)
- Exchangeable potassium (as K2O)
- Exchangeable calcium (as CaO)
- Exchangeable magnesium (in MgO)

4- Description of the technical arrangements for carrying out the spreading

Limitations and risks

Risks related to chemical + biological agents :
- Chemical agents to which employees may be exposed :
- Agents in the incoming waste
- Pesticides
- Gaseous emissions from composting
- CO2, CO
- NH3
- H2S
- Nitrogen oxide
- Volatile organic compounds
- Dust

Biological agents to which employees may be exposed : - Micro-organisms
- Bacteria
- Funghi


4 Vaulx Jardin is a company in Brttiany that seeks to find a sustainable solution to the management and treatment of organic waste.
They design several fertilizers such as :
L’Algo-Forestier®: 100% natural matured and sieved compost combining: Shredded plants, manure, hardwood bark, and seaweed from Brittany. Can be used in Organic Agriculture per European regulations 834/2007 and 889/2008.
For vegetable gardens, trees, and flower beds.


Solagro, IRSTEA. État de l’art des digestats et de leurs procédés de post-traitement - Projet
ANR-10-BIOE_007 DIVA - Rapport Final. Juin 2015

Conclusion : The manure produced should be used optimally to meet the needs of the current
or future crop by providing adequate amounts of nutrients.