Biogas from Agriculture

Agricultural biogas facilities harness organic materials present on farms to produce biogas, a renewable fuel, which is then converted into renewable power via cogeneration or combined heat and power methods. These plants can be configured to process energy crops cultivated for digestion, as well as agricultural residues. Such crops are often ensiled and stored in clamps or hoppers, providing a steady feed to the digester throughout the year. In India, these biogas facilities are often referred to as "gober gas plants.".

Energy Crops and Feedstocks for Biogas Production

Typical energy crops for biogas production can include:

• Maize

• Grass

• Wheat

• Rye

• Triticale

• Crassuleacean acid metabolism (CAM) plants such as pineapples

Alternatively, other organic materials such as waste products may be used including:

• Vegetable waste.

• Glycerol – from biodiesel manufacture

• Palm oil mill effluent

  
  

  

  
  

Agricultural Biogas Plants

Agricultural biogas installations usually comprise multiple digester tanks, often constructed from concrete or metal. These tanks are frequently capped with a dual-layered gas storage bag, lending them a distinctive appearance. The primary digestion tank is responsible for generating the majority of the biogas, while the secondary digestate storage tank yields a lower gas output.

A practical rough estimate indicates that 1 acre (approximately 0.405 hectares) of whole crop maize can yield adequate gas to generate 1 kW of electrical power. In other words, it would necessitate around 500 acres of whole crop maize silage to provide enough feedstock for a 500 kW e digester/gas engine setup.

Economics of Agricultural Biogas

As a common practice, biogas facilities generate income through a gate fee charged for processing waste materials, as well as revenue from selling electricity and heat (or biomethane). Additionally, there's a potential income stream from the sale of soil enhancers.

Agricultural biogas installations often face increased cost sensitivity due to the absence of gate fee revenue. Additionally, there are expenses linked to cultivating feedstock for the digester. These circumstances underscore crucial economic factors:

• The efficiency of the biogas CHP system (conversion efficiency to electricity and heat)

• The availability of the CHP system (number of running hours per year)