Anaerobic Digestion (AD) is a natural process driven by microorganisms which produce biogas and through upgrading, biomethane; two versatile renewable energy carriers that provide electricity, heat and fuel. It is often overlooked that biogas plants also create another product which is at least as valuable as renewable energy, because of its nutrient and organic matter content: digestate. Organic fertilisers have the potential to transform Europe ’ s agricultural sector forever, offering an attractive alternative to commonly used mineral fertilisers. This factsheet briefly outlines the benefits of digestate for the economy, society and our environment.
Digestate can replace mineral fertilisers with environmental and economic advantages. One tonne of artificial fertiliser replaced with digestate saves 1 tonne of oil, 108 tonnes of water and 7 tonnes of CO2 emissions. And the economic savings are staggering, to the point that some new biogas plants, based only in the use of agricultural residues as feedstock, are profitable due to digestate produced and reused in their own farms. “In order to further reduce GHG emissions and improve energy self-sufficiency, organic fertilisers coming from digestate and compost streams -an excellent alternative to mineral fertilisers - should be increasingly deployed. They are far more sustainable than mineral fertilisers, as their production is very low (or even negative) in terms of GHG emissions, what should be acknowledged when calculating anaerobic digestion’s total GHG savings. Also, by using digestate as a fertiliser the carbon content of the soil increases through the remaining and very stable carbon content within digestate, improving soil fertility and field capacity. The latter helps us avoiding desertification. Moreover, plant growth naturally sequesters carbon, which can be stored in the soil once this vegetation, its residues, and products made of it are digested and subsequently used as a fertiliser. In addition, the transport routes of organic fertilisers are short due to the decentralised deployment of biogas plants. Compared to unprocessed organic effluents, digestate has more available nitrogen and it minimises the presence of pathogens as well as invasive species inside it, making this substance a more effective and safer fertiliser. Organic fertilisers from anaerobic digestion only cost a fraction of the price for mineral fertilisers and farmers can even produce these themselves, thereby cutting costs, increasing their revenues and creating jobs in rural area.”