The project Carbon Credits for Sustainable Land Use Systems (CaLas) assessed the potential of organic agriculture for greenhouse gas (GHG) mitigation and for the generation of carbon credits from sustainable land use systems. To this end following activities were conducted within the CaLas project:
Meta-Analysis 1: Enhanced carbon stocks in soils of organic agriculture - A global meta-analysis (published in Proceedings of the National Academy of Science):
Within the first meta-study we conducted a global literature search on soil organic carbon (SOC) datasets from pair wise farming system comparisons of organic and non-organic management. We found 74 eligible, independent studies with 209 comparisons and subjected the data to a meta-analysis to identify differences in SOC contents, stocks and sequestration rates. SOC contents describe the organic carbon content on a weight by weight basis, SOC stocks on a weight by area basis with variable resolution regarding analysed soil depths and sequestration on weight by area and elapsed time since conversion with variable depths and variable time horizons. We also conducted a meta-regression to identify potential drivers for the observed differences. Results from the meta-analysis are quite robust, exhibiting significant differences and higher values for organically farmed soils of 0.18±0.06 percent points (mean±95% confidence interval) for SOC contents, 3.50±1.08 t ha-1 for SOC stocks, and 0.45±0.21 t ha-1 y-1 for sequestration rates. Restricting the analysis to closed organic systems only (i.e. without nutrient inputs from outside the system) and retaining only the datasets with the highest precision in data quality (measured data on soil bulk densities and external annual C and N inputs), the mean difference in SOC stocks was still significant with 1.98±1.50 t ha-1, while the difference in sequestration rates becomes insignificant and shrinks down to 0.07±0.08 t ha-1 y-1. Analysing the closed systems for all data without this quality requirement reveals significant and positive differences in SOC stocks, contents and sequestration rates. Results thus indicate that carbon accumulation is possible in the topsoils of closed organic farming systems. The meta-regression, however, did not allow for clear identification of main drivers for these differences. Some indication that external C inputs and differences in crop rotations could be important may be derived, though. Coverage of data is fairly good for temperate zones, but almost no data from tropical regions is available. Another problem is the sampling depth that covers topsoil only in most studies. Further research is thus required to underpin the observed findings for the entire soil horizon (topsoil and subsoil) and for regions in developing countries which are only poorly represented.
Meta-Analysis 2: Greenhouse gas emissions from agricultural soils under organic and non-organic management – A global meta-analysis (published in Science of the Total Environment)
The second meta-study analysed soil-derived nitrous oxide and methane fluxes under organic and non-organic farm management. It is anticipated that organic farming systems provide benefits concerning soil conservation and climate protection. A literature search on measured soil-derived greenhouse gas (GHG) (nitrous oxide and methane) fluxes under organic and non-organic management from farming system comparisons was conducted and followed by a meta-analysis. Up to date only 19 studies based on field measurements could be retrieved. Based on 12 studies that cover annual measurements, it appeared with a high significance that nitrous oxide emissions from organically managed soils are 486±191 kg CO2 eq. ha-1 a-1 lower than from non-organically managed soils. For arable soils the difference amounts to 472±195 kg CO2 eq. ha-1 a-1. However, nitrous oxide emissions per yield are higher by 52±32 kg CO2 eq. t-1 DM (arable land use). To equalize this mean difference in nitrous oxide emission per yield between both farming systems, the yield gap has to be less than 17%. Emissions from conventionally managed soils are significantly influenced by total N inputs. For organically managed soils other variables such as soil characteristics are more important. This can be explained by the higher bioavailability of the synthetic N fertilisers in non-organic farming systems while the necessary mineralisation of the N sources in organically managed soils leads to lower and retarded availability. The higher methane uptake of 3.1±3.3 kg CO2 eq. ha-1 a-1 for arable under organic management was just not statistically significant. Only one comparative study on rice paddies has been published up to date. It shows reduced nitrous oxide emissions and 1097±242 kg CO2 eq. ha-1 a-1 higher methane emissions under organic management. All 19 retrieved studies were conducted in the Northern hemisphere under temperate climate. Further GHG flux measurements in farming system comparisons are required to confirm the results and close the knowledge gaps obtained so far.
Development and revision of Clean Development Mechanism (CDM) carbon-offset methodologies
After reviewing various existing carbon offset methodologies for their applicability within organic farming systems and after assessing their carbon credit profitability, during the CaLas project, one carbon-offset methodology (“Avoidance of methane emissions through composting”) was revised and a new CDM methodology (“Avoidance of methane and nitrous oxide emissions during biomass burning through mulching”) was developed. Both CDM compliant methodologies were submitted to the United Nations Framework Convention on Climate Change (UNFCCC). They reflect key practices of organic agriculture and offer valuable co-benefits for sustainable development to the target regions. With the new offset methodology “Avoidance of methane and nitrous oxide emissions during biomass burning through mulching” the third largest source for agricultural GHG, i.e. the open biomass burning is tackled. A major innovation of the methodology development is to reduce monitoring costs through the possibility to use organic certification as a source for several data that are needed for monitoring. If this is accepted by the UNFCCC, an organic certifier could become accredited to monitor CDM projects and could realize synergies between the two certification schemes. With the development of the new offset methodology, new types of agricultural projects with important co-benefits in sustainability will be possible under the CDM. The new methodology has been approved by the CDM Executive Board on its meeting (EB Meeting 70) in mid-November 2012.
Pilot project for generating carbon credits
With the Project Design Document (PDD) “San Luis Potosi Sugar Cane Pre-harvest Burning Avoidance and Mulching Project” submitted to UNFCCC, a pilot region in Mexico and a project activity was described which is based on the new CDM methodology (“Avoidance of methane and nitrous oxide emissions during biomass burning through mulching”) developed in the CaLas project. It aims at reducing GHG emissions through avoidance of burning of sugar cane leaves prior to harvest. The sugar cane plantation in this PDD is managed by smallholders and has a total size of 3270 ha. Over the entire crediting period of 7 years (with possible renewal for two additional periods of 7 years each), the average annual estimated emission reductions is 1507 t CO2 eq. y-1.
CaLas IT Tool
An IT tool was developed that allows for the calculation of the mitigation potential of a broad range of agricultural practices to be found in organic farming. The IT tool is decidedly not built to be broadly applicable by laymen. Calculations for some standardised project types can readily be done without further knowledge, but adapting the tool to more specific project situations needs a basic knowledge of the underlying processes and structure of the relevant methodologies. We decided to follow such an approach to reduce the danger of wrong application of these tools, as quantification of the mitigation potential in agriculture is a highly complex and critical task.
Agricultural land management, carbon reductions and climate policy for agriculture (published in the journal Carbon Management)
Besides the work in the context of methodology development, additionally the feasibility of project based offset mechanisms for climate change mitigation policy in agriculture was investigated. We found that generating carbon credits from sustainable/organic land use systems with project based mechanisms is not optimal. There is only few potential for generating carbon credits from sustainable/organic land use systems with project based mechanisms. Barriers for agricultural CDM projects are the high transaction costs (including monitoring costs, etc.), the reliable quantification of emission reductions and a critical size of more than 25000 t CO2 eq. y-1 to make it profitable. Furthermore, sustainable agriculture is multi-functional and provides a wide range of ecosystem and other services besides commodity products, and mitigation performance is only one of those and not necessarily the most important one. These other dimensions of sustainability are however not addressed adequately in current offset mechanisms. Furthermore, financing is challenging as in many agricultural contexts offset mechanisms do likely not work profitably. Some additional funding has to come from other sources. Approaches based on aggregate quantification are better suited for addressing mitigation in agriculture, as they can circumvent the most challenging problems of project based quantification and financing. For certain specific cases, offset mechanisms can however make sense and those should be developed further and applied within the existing institutions. These could be among others the avoidance of pre-harvest burning of sugar cane, as addressed in the new methodology we propose, and agroforestry practices.
To fully harvest the mitigation potential of agriculture, other mechanisms than project based offset mechanisms are needed. One option to overcome the barriers for small-scale projects is the program of activities (PoA) framework which defines broad parameters for project activities that are eligible for inclusion in the PoA and thus allows for bundling several thousand single projects. The PoA framework has thus many features of a more aggregate regional policy than of a project based approach. Such a framework has still to be defined and developed for sustainable/organic land use practices aiming at reducing CO2 emissions and offering valuable co-benefits for sustainable development at the same time. After a first investigation on the most appropriate strategies for implementing climate friendly farming and land use practices it came about that a much more comprehensive analysis of optimal policy instruments for mitigation policy in agriculture is needed to make recommendations for best implementation of sustainable land use systems aiming at reducing GHG emissions and offering other important sustainability criteria at the same time.
Along with the two meta-studies a comprehensive and the worldwide largest data set on soil carbon and GHG emissions of organic/conventional farming system trials has been established. This database established in the CaLas project can be updated and exploited regarding other important criteria of sustainability in terms of productivity, nitrogen and phosphorous efficiency, water use efficiency. Also the potential of adaptation to climate change could be drawn from a further elaborated farming systems database. This should be a task for future activities.
As shown by the two meta-studies there is a lack of data on the climate relevance of farming systems in the developing world. This is essential for the further development and improvement of organic farming systems in these regions. FiBL runs since several years comparative farming system trials in Bolivia (Cocoa production systems), India (Cotton production systems) and Kenia (Vegetable production systems) which can be used for a thorough investigation in this field of research. These long term field trials could be coupled with on-farm trials for a broader impact of the intended research.
The CaLas project enabled a substantial scientific output. Three scientific manuscripts were generated and one new and one revised carbon-offset methodology were submitted to the UNFCCC for approval. In addition, results and insights from the project were presented on various occasions (conferences, journal articles), and contributed to institutional capacity building processes (e.g. for the “Klimastrategie Landwirtschaft” of the BLW).
Coordination and conduction of the main activities
