Life cycle assessment of greenhouse gas mitigation of production and use of bio-methane: sensitivity of effects from N₂O emissions

Figures & data

Table 1. Input data for the LCA for the plant configuration types: state of the art and optimized technology.

			State-of-the art	Optimized technology
Supply with substrates^a	Diesel use	(l/ha)	82.9	82.9
	N-fertilizer	(kg/ha)	141.75	141.75
	Material loss ensilage	(% mass)	15	5
	N2O emissions (soil)	(%^b)	1	1
Fermentation	CH4 leakage reactor	(Vol %)	1	0.5
	Yield of raw gas	(m3/tFM)	200	220
Handling of digestate	CH4 leakage stote	(%)	0	0
	Subsitution of N-fertillizer (mineral)	(%)	70	70
	Subsitution of P,K-fertilizer (mineral)	(%)	100	100
Upgrading	CH4 slip (no aftertreatment)	(%)	2	2
	CH4 slip (aftertreatment applied)	(%)	0.01	0.01
Energy supply	Electricity (reactor)	(kWh el/t FM)	36	36
	Heat (reactor)	(kWh th/t FM)	83	83
	Electricity (PSA)	(kWh el/m3 BG)	0.3	0.3
	Heat (PSA)	(kWh th/m3 BG)	0	0
The differences between the two plant configurations (“state of the art” and “optimized technology” are shown in italics in order to allow a quick overview.
^aExemplary for maize, without accounting for digestate.
^bCalculated in % of nitrogen fertilizer deployed.

Figure 1. The bio-methane process chain.

Figure 2. GHG factors of the process chain bio-methane: sensitivity analysis. Variant 1: increased methane leakage in reactor (1.5% instead of 1%); Variant 2: increased methane slip in PSA (no after treatment, slip of 2% instead of 0.01%); Variant 3: digestate storage not completely covered – moderate emissions of 2.5% of gas stored. Red line: GHG emissions of natural gas.

Figure 3. GHG balance of bio-methane from different substrates in regionally adjusted crop rotation systems

Figure 4. Sensitivity analysis: effects of different assumptions of N₂O emissions to the overall GHG balance in the state-of-the-art biogas plant. Variant 1: increased methane leakage in reactor (1.5% instead of 1%); Variant 2: increased methane slip in PSA (no after treatment, slip of 2% instead of 0.01%); Variant 3: digestate storage not completely covered – moderate emissions of 2.5% of gas stored. Red line: GHG emissions of natural gas.

Table 2. Composition of biogas substrates at the five locations.

	Maize	Rye	Sorghum	Triticale	Grass^a	Barley
Dornburg	×	×	×
Gülzow	×	×		×
Güterfelde	×	×	×
Ascha	×	×			×
Soest	×		×			×
^aMixture of hairy vetch (vicia villosa), crimson clover (trifolium incarnátum) and Italian ryegrass (lolium multiflorum).