13 Jan 2017

The feasibility of biogas on Australian vegetable farms

Kym Whiteoak, Carl Larsen and Anne-Maree Boland

There is significant interest within the vegetable industry in maximising efficiency and productivity across the production process, including maximising value from waste streams.

Biogas is methane and carbon dioxide produced from the bacterial degradation of organic waste.  Using anaerobic digestion, the process produces electricity, heat and a residual organic product that can be used on-farm as an organic fertiliser.

This study was commissioned to explore in more detail the feasibility of biogas on Australian vegetable farms. Extensive consultation with industry was undertaken, including the development of a number of case studies. The key findings from this analysis were:

  • Feasibility is highly variable
  • Potentially feasible for larger operations
  • Other factors contribute to feasibility such as crop type, consistency of waste supply and energy use, and the current costs of waste management
  • ‘Cluster’ model (the cooperation of a number of vegetable farms) adds complexity
  • Technical feasibility a reflection of cost
  • Regulatory burden not excessive
  • Digestate use and management will require careful consideration.

The feasibility of biogas on-farm will depend upon the specific context of each operation. However, the following key factors will influence biogas feasibility on-farm:

  • Scale of operation: the cost-effectiveness of biogas generally increases with scale, an input volume of 25 tonnes per day or more would warrant further consideration of biogas on farm
  • Type of waste: different organic wastes produce different volumes of biogas per unit[1],[2]
  • Electricity value: retail tariffs vary significantly by type of site and to some extent by jurisdiction
  • Nature of current waste management: biogas value will be influenced by the costs and revenues associated with a farm’s current waste management practices
  • Consistency in feedstock and electricity use: in general, consistency in both waste production and electricity use are preferred features to highly variable waste supply and electricity use.

[1] Testing typically costs around $2,000-$3,000 per waste type, and the biogas efficiency of different waste types is often commercial in confidence information.

[2] However, lettuce may be combined with other waste types to produce a high-methane mix.

This paper was presented at the Bioenergy Australia Conference 2014 proceedings, Adelaide (2014).