Life cycle assessment of biofuels in the European Renewable Energy Directive: a combination of approaches?

Figures & data

Figure 1. System boundaries of this LCA study.

Table 1. Properties of the combined heat and power boilers assumed in this study.

CHP boiler	Overall thermal efficiency (%)	Heat to power ratio	Rating (MW)	Excess electricity (kWh/GJ bioethanol)
Natural gas-fired	85	1.93	34	24.0
Straw-fired	64	1.26	54	39.9

Table 2. Allocation parameters assumed in this study.

Co-product	Unit	Energy content (GJ/unit)	Notes	Economic value (£/unit)	Notes
Wheat	Tonne	13.7	Based on the Milne equation^a	188	Average shadow price for wheat in 2012, UK^a
Wheat straw	Tonne	13.7	Based on the Milne equation^a	49	Average shadow price for wheat straw in 2012, UK^a
Bioethanol	Tonne	26.8	^b	540	^c
DDGS	Tonne	16	^d	180	^e
Electricity	kWh	0.0036		0.149	^f

^aWhittaker (2013).

^bEUCAR, CONCAWE, and JRC (2006).

^cBrander and Wylie (2011).

^dAlberichi and Hamelinck (2010).

^eYan and Boies (2013) – average between 2008 and 2011.

^fUK Power (2014).

Table 3. Electricity emission factors for natural gas- and straw-based electricity based on the assumptions in Section 2.1.

Fuel source	Carbon dioxide	Methane	Nitrous oxide	Total GHG
	(kg CO2 eq./kWh)	(kg CH4/kWh)	(kg N2O/kWh)	(kg CO2 eq./kWh)
Natural gas	0.356	7.4 E10^−4	6.6 E10^−6	0.375
Straw	0.012	3 E10^−6	8 E10^−8	0.012

Figure 2. Breakdown of sources of GHG emissions from bioethanol production from wheat according to the LCA methods studied here.

Table 4. Results generated according to the four LCA methodologies examined in this study.

Fuel source for processing	Allocation method	GHG emission result (kg CO2 eq./GJ)	GHG savings compared to gasoline (%)
Natural gas	Substitution
	Straw removed	−63.69	176.0
	Straw incorporated	−59.38	170.9
	Price
	Straw removed	44.20	47.3
	Straw incorporated	50.36	39.9
	Energy
	Straw removed	33.40	60.1
	Straw incorporated	44.72	46.6
	RED
	Straw removed	62.26	25.7
	Straw incorporated	66.56	20.6
Straw	Substitution	−91.92	209.7
	Price	38.55	54.0
	Energy	35.01	58.2
	RED	60.19	28.2

Table 5. Results from the study depending on straw removal or incorporation in the reference system.

Reference system	GHG saving from using straw in-house (kg CO2 eq./GJ)
	Straw removed	Straw left onsite
Allocation method
Substitution	28.2	33.9
Price	5.6	13.2
Energy	−1.6	11.1
RED	2.1	7.9

Whittaker, C. (2013). The importance of life cycle assessment methodology in the regulation of biofuels (PhD thesis). University of Bath, Bath.

 Google Scholar

EUCAR, CONCAWE, & JRC. (2006). Well-to-wheels analysis of future automotive fuels and powertrains in the European context (No. Version 2b).

 Google Scholar

Brander, M., & Wylie, C. (2011). The use of substitution in attributional life cycle assessment. Greenhouse Gas Measurement and Management, 1(3–4), 161–166. doi:10.1080/20430779.2011.637670

 Google Scholar

Alberichi, S., & Hamelinck, C. (2010). Annotated example of a GHG calculation using the EU Renewable Energy Directive methodology (No. Project Number: PEGENL083540). Ecofys.

 Google Scholar

Yan, X., & Boies, A. M. (2013). Quantifying the uncertainties in life cycle greenhouse gas emissions for UK wheat ethanol. Environmental Research Letters, 8(1), 015024. doi:10.1088/1748-9326/8/1/015024

 Google Scholar

UK Power. (2014). Electricity running cost calculator | electricity prices | electricity costs. Retrieved July 15, 2014, from http://www.ukpower.co.uk/tools/running_costs_electricity#.U8U651JY_Fk

 Google Scholar