The Carbon and Global Warming Potential Impacts of Organic Farming: Does It Have a Significant Role in an Energy Constrained World?

Abstract

About 130 studies were analyzed to compare farm-level energy use and global warming potential (GWP) of organic and conventional production sectors. Cross cutting issues such as tillage, compost, soil carbon sequestration and energy offsets were also reviewed. Finally, we contrasted E and GWP data from the wider food system. We concluded that the evidence strongly favours organic farming with respect to whole-farm energy use and energy efficiency both on a per hectare and per farm product basis, with the possible exception of poultry and fruit sectors. For GWP, evidence is insufficient except in a few sectors, with results per ha more consistently favouring organic farming than GWP per unit product. Tillage was consistently a negligible contributor to farm E use and additional tillage on organic farms does not appear to significantly deplete soil C. Energy offsets, biogas, energy crops and residues have a more limited role on organic farms compared to conventional ones, because of the nutrient and soil building uses of soil organic matter, and the high demand for organic foods in human markets. If farm E use represents 35% of total food chain E use, improvements shown of 20% or more in E efficiency through organic farm management would reduce food-chain E use by 7% or more. Among other food supply chain stages, wholesale/retail (including cooling and OPEN ACCESSSustainability 2011, 3 323 packaging) and processing often each contribute 30% or more to total food system E. Thus, additional improvements can be obtained with reduced processing, whole foods and food waste minimization.

Ecosystem Services in Biologically Diversified versus Conventional Farming Systems: Benefits, Externalities, and Trade-Offs

“…Over the last 15 years, many attempts have been made to measure the global-warming potential of conventional and diversified farming systems by calculating relative energy use, energy-use efficiency, and the outputs of key greenhouse gasses including carbon dioxide (CO 2 ), methane (CH 4 ), and/ or nitrous oxide (N 2 O) (Lynch et al 2011). In a major review of approximately 130 studies, Lynch et al (2011) analyzed farm-level energy use and global-warming potential of organic and conventional farming systems, including field, fruit, and vegetable crops, and beef, hog, poultry, and dairy production.…”

Diversification practices reduce organic to conventional yield gap

“…Organic agriculture is defined as having no synthetic inputs, but organic farms may or may not practise the full suite of cultivation techniques characterizing sustainable agriculture [21,25]. Although the terms 'organic' and 'sustainable' agriculture are not equivalent, studies of organic agriculture have revealed better performance than conventional systems on some (but not all) sustainability metrics, including species richness and abundance, soil fertility, nitrogen uptake by crops, water infiltration and holding capacity, and energy use and efficiency [26][27][28][29][30][31][32]. Here, we provide the most comprehensive calculation of the yield gap between organic and conventional agriculture, building on the work of others [33][34][35][36].…”

System-level approach needed to evaluate the transition to more sustainable agriculture

“…This would also contribute to the profitability of these systems by reducing the costs of inputs such as pesticides [18] or managed honeybees [19]. Expanding organic and diversified practices may also enhance food security by reducing reliance on fossil fuels owing to higher energy efficiency [20] and managed honeybees through promoting wild pollinator populations [21]. At the same time, organic soils also have higher water storage and infiltration, leading to higher resilience to severe weather conditions than in conventional systems [22].…”

“…Further, he fails to take a large-scale, systems perspective in his assertion that organic farms create more greenhouse gas emissions per unit of yield, because he considers only the gas fluxes from soils. When the entire system is considered, organic farming systems have on average higher energy efficiency and lower greenhouse gas emissions per farm product than conventional farms [20]. The lower-energy efficiency in conventional farms is primarily owing to nitrogen fertilizers, which are highly energy intensive to produce [36].…”