Towards a Full Circular Economy in Biogas Plants: Sustainable Management of Digestate for Growing Biomass Feedstocks and Use as Biofertilizer

Linas Jurgutis,Jurgita Cesevičienė,Jonas Šlepetys,Alvyra Šlepetienė

doi:10.3390/en14144272

Linas Jurgutis, Jurgita Cesevičienė + Show 2 more

Open Access

https://doi.org/10.3390/en14144272

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Abstract

The digestate is a prospective biofertilizer and potential source of income for many biogas plants worldwide. However, its actual impact on the soil properties and biomass yield is still unexploited. The different digestates from eight agricultural biogas plants were researched in terms of their chemical composition and the fertilizing potential. The results obtained from digestate chemical analysis indicate that the digestate biomass had large amount of nitrogen (up to 73 g kg−1 fresh mass) and potassium (up to 25 g kg−1 fresh mass). The value of the digestate was estimated in the range of 2.88–7.89 EUR Mg−1 for liquid digestate and 7.62–13.61 EUR Mg−1 for solid digestate based on the commercial fertilizer market price of nitrogen, potassium phosphorus, organic carbon, Cu, Zn, Fe and Mg. The digestate produced at the 1 MW biogas plant is worth EUR 941–2095 per day in addition to energy sales income. The application of digestate on low-fertility land in areas close to the biogas plant allows the production of up to three-fold more biomass suitable for biogas production. The digestate’s application on semi-natural grass biomass production in the low-fertility soils near the biogas plants could be an alternative strategy for the biogas plant feedstock portfolio diversification.

Highlights

The global increase in energy demand together with ambitious greenhouse gas emission reduction plans creates the opportunity for constant renewable energy capacity growth.The shift from fossil fuel-based energy production to renewable energy generation can partly be achieved by increased biobased energy generation
Digestate can potentially be used as biofertilizer for higher yields of biomass feedDigestate can potentially be used as biofertilizer for higher yields of biomass feedstock stock production near to the biogas power plant
If digestate was sold as a fertilizer product, the average biogas plant could generate additional income revenues of EUR 941–2095 d−1 based on the minimum and maximum digestate values determined

Summary

Introduction

The global increase in energy demand together with ambitious greenhouse gas emission reduction plans creates the opportunity for constant renewable energy capacity growth. The shift from fossil fuel-based energy production to renewable energy generation can partly be achieved by increased biobased energy generation. Biogas-based energy production increases the base load renewable energy production. Biogas is an alternative energy source to natural gas. The current natural gas grid infrastructure can be adapted for green and renewable biomethane injection and transmission internationally. The use of biogas to partly replace natural gas has the potential to reduce imports of energy resources in many countries. Local green biomethane production would allow the development of energy independence for many regions and countries worldwide

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