Carbon footprint of black peat from degraded peatland previously used for agriculture in Germany
On a worldwide scale, drained peatlands contribute substantially to anthropogenic greenhouse gas (GHG) emissions. Reducing GHG from drained peatland is the most space- and cost-effective climate change mitigation option within the land use and agricultural sectors. Peat, particularly black peat, is currently a major compound in substrates for horticulture, where it cannot be immediately replaced One option is to extract black peat from degraded peatland, which cannot be rewetted. In order to calculate the carbon footprint (CF) a life cycle approach is applied and three scenarios are defined. The carbon footprint varies widely for nutrient-rich peat in the best-case 70, default 107 and worst-case 161 kg CO2eq per m³ stored black peat. For nutrient-poor peat the carbon footprint is significantly lower best case 49, default 64 and worst case 70 kg CO2eq per m³ stored black peat. If German national EFs are used, the CF values are even lower, 28, 45 and 70 kg CO2eq per m³ stored black peat. The difference between nutrient-rich and nutrient-poor peat is caused by the respective carbon density provided in the IPCC guidelines. Despite substantial differences in diesel consumption and extraction rate, the carbon footprint of black peat extracted from degraded peatlands is dominated by two factors, the GHG emissions during black peat storage and the period assumed for land restoration. Surprisingly little is known or reported in the literature concerning these factors. In order to get more precise results, the existing knowledge gaps, particularly methane emissions during black peat storage, have to be examined. In order to calculate the carbon footprint of black peat from degraded peatland in a transparent and reproducible manner, a conceptional model and a decision tree for selecting area-based EFs is presented.