LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 2A: LAND USE 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Organic farming without fossil fuels – LCA of energy self-sufficiency
Cecilia Sundberg 1,* , Marie Kimming 1 , Åke Nordberg 1,2 , Andras Baky 2 , Per-Anders Hansson 1
1 Department of Energy and Technology, Swedish University of Agricultural Sciences
2 JTI – Swedish Institute for Agricultural and Environmental Engineering
Corresponding author. E-mail: cecilia.sundberg@slu.se
ABSTRACT
One principle of organic farming is the use of renewable resources, yet it depends on fossil energy. Systems for supplying organic
agriculture – one arable farm and a system for milk production - with heat, power and fuel generated from biomass produced on its
own land, and the consequences of such production were investigated. Biomass energy systems included power, heat and ethanol
from straw and biogas generating power, heat and fuel from ley, manure and straw. For the arable farm, straw or ley from the crop
rotation was sufficient for energy supply for farm activities. For milk production, biogas from manure could supply about two thirds
of the energy demand of the farm and there was straw to supply the remainder. GHG emissions were reduced in all scenarios compared
to the fossil reference. The GHG results were sensitive to assumptions on soil carbon initial content and turnover.
Keywords: biogas, biomass, CHP, renewable energy, straw
1. Introduction
Even though organic farms aim to lower the environmental impact from food production and rely mainly
on renewable, locally available resources, they still depend on fossil fuels for energy supply to production
processes. Organic farms could increase their credibility as a sustainable alternative if renewable resources
were used for producing energy for the farm. The agricultural sector is also considered to have the largest
potential to contribute to a higher share of renewable energy in the EU (EEA 2006).
The technical development of systems for energy generation based on biomass has progressed rapidly
over the last few years and the number of small-scale applications suitable for farm use has increased. Dairy
farms have access to readily available manure which can be used for biogas production. Biogas can be used
for heat and power production or is upgraded to vehicle fuel. Hydrolysis of cellulosic substrates is the next
generation of ethanol production, projected to replace the much debated production of ethanol from food
crops such as sugar or starch products.
This paper summarizes the findings our research on how to supply organic agriculture with energy produced
on its own land, and the environmental consequences of such production. The purpose of this study
was to assess the self-sufficiency potential, greenhouse gas emissions and energy balance of crop production
(described in detail in Kimming et al., 2011) and milk production (Kimming et al., 2012) in a renewable
energy supply systems mainly based on bioenergy, compared with systems based on fossil fuels.
2. Method and scenario description
2.1. LCA approach and functional unit
Since the goal was to investigate the impact of changing to a new energy supply system, consequential
LCA was used for these studies. The substitution method was used to avoid allocation.
The functional unit (FU) used was 1 kg ECM (energy-corrected milk) at the farm-gate for the milk study.
For the arable farm, the FU was the total supply of energy (heat, electricity and vehicle fuel for the 200 ha
organic farm for 1 year. The impact categories were energy balance and global warming potential
(GWP100).
2.2. Agricultural production systems
The milk farm was assumed to have 100 dairy cows, with an average of 84 animals being milked every
day. Data on milk production are presented in Table 1. The farm was assumed self-sufficient in organically
produced forage (Table 2).
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