Net-Energy Analysis of Integrated Food and Bioenergy Systems Exemplified by a Model of a Self-Sufficient System of Dairy Farms

Abstract

Agriculture is expected to contribute in substituting of fossil fuels in the future. This constitutes a paradox as agriculture depends heavily on fossil energy for providing fuel, fodder, nutrients, and machinery. The aim of this paper is to investigate whether organic agriculture is capable of providing both food and surplus energy to the society as evaluated from a model study. We evaluated bioenergy technologies in a Danish dairy-farming context in four different scenarios: (1) vegetable oil based on oilseed rape, (2) biogas based on cattle manure and grass-clover lays, (3) bioethanol from rye grain and whey, and (4) a combination of (1) and (2). When assessing the energetic net-contribution to society from bioenergy systems, two types of problems arise: how to aggregate non-equivalent types of energy services and how to account for non-equivalent types of inputs and coproducts from the farming? To avoid the first type, the net output of liquid fuels, electricity, useful heat, and food were calculated separately. Furthermore, to avoid the second type, all scenarios were designed to provide self-sufficiency with fodder and fertilizer and to utilize coproducts within the system. This approach resulted in a transparent assessment of the net-contribution to society, which is easy to interpret. We conclude that if 20% of land is used for energy crops, farm-gate energy self-sufficiency can be achieved at the cost of 17% reduction in amount of food produced. These results demonstrate the strong limitations for (organic) agriculture in providing both food and surplus energy.

Smart integration of food and bioenergy production delivers on multiple ecosystem services

“…Allocating part of the cereal area to green manuring in order to produce feed for biogas production resulted in a decreased area for cereal production. Similar results were published by Pugesgaard et al (2014) and Markussen et al (2015) who found that allocating part of the land to energy production decreased the total output of food. However, if grasses are cultivated on less productive fields or if yields are increased by improving soil fertility, the impact is not as great as the share of the reduced cereal area would imply.…”

Nested circularity : Localized food in a globalized world

“…Allocating part of the cereal area to green manuring in order to produce feed for biogas production resulted in a decreased area for cereal production. Similar results were published by Pugesgaard et al (2014) and Markussen et al (2015) who found that allocating part of the land to energy production decreased the total output of food. However, if grasses are cultivated on less productive fi elds or if yields are increased by improving soil fertility, the impact is not as great as the share of the reduced cereal area would imply.…”

How contradictory EU policies led to the development of a pest: The story of oilseed rape and the cabbage stem flea beetle

“…Currently, the production of biofuel from crops still requires the use of fossil fuels during crop production (Dalgaard et al, 2001), and other factors including various social, economic, environmental and technical issues need to be overcome to make the production process more sustainable (Oumer et al, 2018). However, biofuel production from OSR has been calculated to have a positive net energy balance (Kusek et al, 2016) and can also contribute towards circular, self-sufficient systems in terms of energy requirements (Markussen et al, 2015).…”