Biogas Plants (Biodigesters)

The bio-digesters are «biological engines» allowing the transformation of (liquidor dry) organic matter (liquid or dry) into biogas and stabilised organic fertiliser.


Biogas plants are facilities with three purposes:

  1. Treat the organic matter (liquid or solid) by biological process.
  2. Generate a renewable natural gas for energy usage.
  3. Stabilize the organic material for its better use as fertilizer.

Bio-digesters convert organic matter carbon into methane (CH4) and carbon dioxide (CO2). The macro and micro nutrients are not removed by the anaerobic digestion and both treated effluent as well as sludge can be valorized as liquid or solid biofertilizers as part of the BIOTEC concept of Zero Discharge Milling (ZDM).



Main biodigesters models developed by BIOTEC:

  • UASB = Upflow Anaerobic Sludge Blanket
  • RAC ® = Contact Anaerobic Reactor
  • RAFAC ® = Contact Upward Flow Anaerobic Reactor
  • RAS ® = Dry Anaerobic Reactor (Visit

Composting plants

Visit our EFB-POME co-composting

Composting is a technique of processing (solid) organic by-products.

The objectives of the composting process are:
  • Reduce the volume and the weight of material to be transported
  • Stabilize organic matter to turn it into compost
  • Replace chemical fertiliser in the field
  • Control odours
  • Recycle the nutrients to the soil
  • Evaporate wastewater and sludge

Depending on raw material, land available, environment, weather conditions, objectives and industry policy, BIOTEC engineers composting plants by front turner (traditional system), by side turner and/or by forced aeration.


  1. FT: Traditional system with front turning
  2. LT: Alternate system with side turning which allows greater height of piles and avoid spaces between piles
  3. FV: Forced aeration. In this system it is not necessary to proceed to turning as long as the material is sufficiently loose
  4. (Visit our EFB-POME co-composting)

Liquid Organic fertilisation systems

Visit our Brochure Fertirrigation

Liquid fertilization with raw or treated effluent is one of the ways to aceive the concept of “Zero discharge” to the environment. Agronomical and agricultural engineering are a complement to environmental and sanitary engineering. Fertilisation with fresh or degraded waste is already a common practice in agriculture all around the world. Liquid Organic Fertilisation is less known but equally important.

Typical spray or drip liquid application technologies can often be used, as well as spraying trucks. In some special cases, like citrus and oil palm, BIOTEC engineers innovative solutions for effluent application. This is the case of "FORLIM"® (Liquid Organic Fertilisation Monitored System) that allows the a SCADA monitored application of treated effluent and sludge from the bio-digesters in a controlled fashion on the plantations. SCADA and GIS (Geographical Information System) allow online control and tracking of the fertilisation process.

The FORLIM technology generate periodic reports on fertilisation for the management and/or environmental authorities.

Dosage of nutrients per hectare per year are similar to the dosage used for chemical fertilisation.

  • Zero discharge to rivers and water bodies
  • Providing and adding value to anaerobic sludge and effluents
  • Replacement of chemical fertiliser
  • Improvement of the soil
  • Yield Increase in performance
  • Better resistance to parasitism (illnesses)
Order of magnitude:
Crop Dosage (liquid organic fertilizer).
OIL PALM: 100 - 300 m3/ha-year
SUGARCANE: 50 - 300 m3/ha-year
CITRUS: 1000 - 2000 m3/ha-year
(Visit our Brochure Liquid Fertilization)


In many cases, the Environmental Authorities do not allow any discharge to the river (it happens frequently with cane vinasses) or ask so high COD, BOD, N or P removal rates that the wastewater treatment plant’s CAPEX and OPEX make the agribusiness no competitive anymore.

With its technological partner SSP from India (, a company specialized in evaporation and drying (for food, aromas and effluents), BIOTEC developed the concept of ZERO DISCHARGE MILLING thanks to effluents BIO-EVAPO-DRYING.

BIOTEC/SSP developed three technologies:

   1. Co-composting with solid biomass.

     Example: Vinasses with sugarcane mud / POME with EFB in the palm oil industry (visit our co composting brochure).

   2. Raw effluent evaporation (in Multi-effect evaporators - MEE) and Drying Example: Transformation of POME into Animal feed (powder) Very convenient is exhaust steam is available after steam turbines.

   3. Bio-evapo-drying The principle is the following:

     (Visit our Brochure Biodrying)
  • Stage 1: Methanisation of the effluents to generate fuel gas and to concentrate it in nutrients (by a factor 3 to 4, on average). Consequently, an effluent with 3% K2O, for example, ends up having 12%.
  • Stage 2: Evaporation of the methanized effluent, using the biogas as fuel. The evaporator delivers a "digestate" concentrated in nutrients, which 25 to 40% dry matter (DM) depending on the case. The evaporators are MEE (Multi-Effect Evaporators) with low energy consumption.
  • Stage 3: Drying the "digestate”, until producing a very fine powder with only 5% humidity. The dryers are "SPRAY DRYERS" or “PADDLE DRYERS” (mixing MEE concentrate with sludge cake) and use the same biogas as fuel.

The final product is a bio-fertilizer powder, with 40 to 50% stabilized (digested) organic matter and 30 to 40% macronutrients (nearly similar to a chemical fertilizers).

We have the possibility of separating the final product into a soluble fertilizer, which is usually sold as powder, and an insoluble one, which is usually marketed as granules.

(Visit our Brochure Bio-Evapo-Drying)

Consequently, the "bio-drying" allows:

  • Avoiding any discharge other than crystallized condensed water
  • Achieving energy self-sufficiency of the evapo-drying process, at least for high COD effluents, such as vinasses and palm effluents
  • Producing a high added value marketable bio-fertilizer

The ideal application cases for BIO-DRYING are the distilleries vinasses (spent wash) and palm oil mill effluents, due to their high COD and the strict normativity in some countries like India and Malaysia. SSP has the world leadership in evaporation and drying of methanized effluents and has already equipped 14 distilleries in India in the last 8 years.

SSP is also a leader in the evapo-drying of complex, dangerous or delicate effluents such as pharmacy effluents or landfill leachate. In these cases of effluents with low organic load, we usually choose to evaporate and dry the crude effluent, without prior methanization, as the production of biogas would anyway not be sufficient to fuel the equipment and as the objective is not to produce a biofertilizer but only solve a major environmental problem.



When the agroindustry has not a defined idea of the project to implement to treat and valorize effluents and waste, BIOTEC provides the service of “CONCEPTUAL ENGINEERING” to present the different options, with their respective advantages, disadvantages and approximative costs.


BIOTEC designs, builds, implements and supervises its solutions on an industrial scale.

The implementation of these projects can be done in two ways:
  1. Full/partial turnkey : BIOTEC is responsible for the entire project, from the design and construction of the plant to the commissioning. For partial turnkey, the client is responsible for civil works and the direct purchase of certain equipment.
  2. Integral Engineering (EPC-EPCM): Includes: design, supervision of works, inoculation, start-up. Advice on purchases and / or project management is optional (= project management).


BIOTEC uses to operate its plants for up to two years, or to support its clients in the routine operation all the time required. By this way, BIOTEC commits with the KPI for a long period and the client benefits from its experience and from technology upgrading year after year. It is definitively more comfortable for (biogas-composting-fertigation or bio-drying) plants operators to have a permanent support for the designer (physical or remote).


BIOTEC operates plants under two models:

  1. Management: BIOTEC participates in the operation with its own staff, leading and training the client’s team.
  2. Supervision: On-line monitoring (SCADA system) with periodical audits.
BIOTEC designs and builds with operation in mind.

4. CDM Projects:

BIOTEC has been world leader in CDM projects between 2006 and 2012, especially in the palm oil industry. Eight BIOTEC biogas projects have been registered as “CDM” (Clean Development Mechanisms). The first one (# 392 on UNFCCC (United Nations) register), has been operated by BIOTEC for 5 years, including the attendance of the yearly UNFCCC verifications; the others for an average of two years. While operating these CDM plants, BIOTEC always get the maximum number of CERs (Certified Emission Reduction) calculated and allowed by the PDD (Project Design Document).