Building a sustainable project

To guarantee the success of its anaerobic digestion projects, Evergaz, via its specialised consultancy firm Ledjo Energie, carries out feasibility studies which integrate technical as well as social, environmental, legal and financial parameters.

The feasibility study of every anaerobic digestion project involves several aspects:

  • The implementation of the sourcing plan;
  • The study of sources for the identification, qualification and securing of source materials;
  • The study of the recovery of the digestate produced;
  • The study of the energy needs to recover the energy produced;
  • The preliminary technical dimensioning of the project;
  • The environmental footprint of the operation;
  • The latest developments in applicable regulations;
  • The economic analysis forecast.

As part of these studies, a number of scenarios are analysed. To comply with ADEME's specifications, Evergaz favours solutions that minimise the environmental impact, respond to the needs of local populations while optimising economic performance.

While digestible by-products are identified in the sourcing plan, the purpose of the study of sources is to characterise these by-products more accurately: quantity, volume, type of products, quality and seasonality. To assess the methanogenic potential and safety of each material, Evergaz works with a partner laboratory and uses its own database of 1,400 products, constantly enhanced by feedback from its own anaerobic digestion units.


  • Assess the methanogenic potential as well as the technical and economic constraints of every by-product identified
  • Determine the resources to be implemented to facilitate the transport, storage and treatment of the products selected
  • Evaluate the costs of this implementation according to the envisaged location sites
  • Propose one or more sourcing scenarios
  • Estimate energy productivity and dimensioning: biogas, electricity, heat or biomethane.

The efficiency of the energy produced and the agricultural value of the digestate depend on the quantity and quality of the sources. To optimise the performance of the sources and ensure a continuous volume of input, the potential organic waste is identified within a radius of 20 to 40km of the project. At this stage, the impact of transport on the profitability and acceptability of the project is taken into account.

Everything is transformed in anaerobic digestion projects: while biogas is transformed into energy, the digestate is also used as a natural fertiliser at the end of the cycle. This is why the feasibility study includes the analysis of the digestate, for characterisation and identification purposes, based on its agricultural value and recovery opportunities.


  • Assessment of the total volume of digestate produced
  • Assessment of the product's agricultural quality
  • Assessment of the agricultural value of the digestate by type of crop rotation according to the performance objectives, quantities and types of product currently spread
  • Identification of the technical land spreading constraints and suggestions for appropriate technical solutions
  • Assessment of the required spreading surface areas
  • Study of the exchange conditions between agricultural materials and digestates

For every biogas recovery scenario envisaged, and based on the sourcing plan, the anaerobic digestion facilities can be designed by integrating the potential input volume, the size of the unit and the output volume, including the nature of the recovery processes.


  • Creation of a schematic diagram of the facility
  • Description of the facility and its principal constituent parts
  • Assessment of the most suitable anaerobic digestion method: dry or liquid, biogas, electricity, heat production assessment, assessment of the site's own electricity and heat consumption, etc.
  • Dimensioning assessment according to the technology best suited to the source selected
  • Calculation of the material and energy balance
  • Provisional layout map

As anaerobic digestion, by its very nature, contributes to sustainable development, the impact of the project on the environment is reviewed from the feasibility study stage.


  • Assessment of the gain generated by fossil fuel replacement: assessment of the savings (kWh/year) compared with the current situation, assessment of the reduction in CO2 emissions in metric tons/year compared with the current situation
  • The greenhouse gas balance will be determined using the DIGES method, a tool developed by ADEME (French Environment and Energy Control Agency) to quantify the greenhouse gas emissions of an anaerobic digestion facility.

At every stage of the feasibility study, the applicable regulations are integrated into the scenarios, including:

  • the legislation on waste, with the traceability obligation in terms of animal waste (European regulation on animal by-products: health approval) and WWTP sludge
  • the requirements applicable to classified installations for environmental protection (ICPE: sections 2781, 2160, 2910, etc.)
  • regulations on the future of digestates (spreading plan) and biogas recovery
  • energy sales conditions and procedure - electrical connection, connection in the event of an injection of purified biogas (biomethane) into the natural gas network

The feasibility study includes the analysis of the future unit's provisional investment costs and operating costs, so that the profitability potential can be accurately estimated.

This technical and financial information helps select the most economically, technically and environmentally appropriate scenario.

Evergaz carries out complementary studies according to the specific needs of the project.

These include:

  • Study on the implementation of a solid digestate composting platform
  • Study on the implementation feasibility of a fodder drying unit linked to a cogeneration unit
  • Study on the territorial energy needs consistent with the thermal energy produced by a cogeneration unit
  • Study on the territory's energy requirements
  • Determination of the most suitable biogas recovery method (cogeneration, boiler, injection, NGV, etc.)