Production of electricity and soil enhancer through anaerobic digestion of agricultural waste
Currently the management practices of livestock manure involve the collection and storage in livestock units or the spreading in the fields. The waste include manure generation from pig or poultry livestock farms, cheese whey and olive facilities. The aforementioned practices constitute significant hazards due to the increased smelling and fire causing. Additionally most of the nutrients are lost and the CO2 footprint is high in the areas were such farms are located.
The facility is private and collects locally available farm manure for free. The manure is transported by trucks in the facility and is digested on-site. The produced biogas is utilized in a generator unit, while the digestate is composted and returned to the nearby fields as soil amendment.
The main stakeholders and beneficiaries are owners of the facility (who also own livestock farms and cultivations) and use the vast majority of the generated fertilizer in their cultivations. In addition, neighboring farming facilities are collaborating offering their facilities’ waste to the biogas facility without the obligation of payment. This constitutes a "win-win" situation in the area since farmers are disposing their waste in a sustainable manner and facility operation minimise the local CO2 impact. All aforementioned as well as local population are the beneficiaries. Finally yet importantly, the energy generated by the facility is provided to the national grid (under an agreed cost per kWh).
The facility required 3.9 million euros as initial set up cost. The cost was partly covered by the European funding tool JESSICA.
It runs on a 24h basis by approximately 10 persons (workers, engineers and administration staff).
Evidence of success
In 2017 the facility produced 8,5 ΜWh renewable electricity, while CO2 savings were estimated at around 494.700 kg. During that year the facility processed:
• 70.000 t liquid cow manure
• 5.000 t poultry manure
• 1.000 t pork manure
• 6.000 t cheese whey
• 2.000 t olive mill by-products
The cost of residue transportation is high. Since the facility cannot undertake it, they only serve nearby farms. Education and awareness of primal sector stakeholders is required to understand this waste impact (and potential) and eventually undertake the transportation cost to the facility.
Potential for learning or transfer
The plant has operated since 2016 (trial) but officially started its operation and the electricity generation on early 2017. Biogas production helps to decrease the greenhouse gas emissions and through digestate composting nutrients return to the fields. The carbon footprint of the electricity production alone is 494,7 tons CO2 eq/a negative. The practice may be transferred to other agricultural areas with both livestock farms and cultivations exist to solve the problems related to disposal of biological waste, raise awareness and inspire farmers to run their facilities in a more sustainable manner.
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