Wood in peat fuel: Impact on the reporting of greenhouse gas emissions according to IPCC Guidelines

The production and use of peat fuel is a significant source of emissions in the Finnish national greenhouse gas inventory. About 10-15% of the total greenhouse gas emissions in Finland can be attributed to the production and combustion of peat. The peat fuel contains about 2.6% (range 1.2 to 12.5%, calculated from the energy content of the peat) non-decomposed large pieces of wood: stem wood and stumps. Earlier, this wood in peat was separated from the peat before combustion because the large woody pieces caused problems in the combustion process. Nowadays, the large pieces of wood in peat fuel is increasingly crushed, milled, and combusted with the rest of the peat. The emissions from the non-decomposed large pieces of wood in peat have been treated differently in the inventory, depending on the practice. When the wood in peat has been separated from the peat before combustion, it has been treated as a renewable biomass fuel and the CO2 emissions have not been included in total national emissions. In cases where peat including wood has been combusted without separation, the emissions from the wood in peat have been treated as emissions from peat. Peat is treated comparable to fossil fuels in the inventory and CO2 emissions are included in national total emissions. Wood in peat is on average as old as other plant material of which the peat is formed. The time scale to mitigate the climate change is of the order of 100 to 300 years according to the IPCC stabilization scenarios. If the turnover rate of a carbon pool exceeds this time scale, the use of this pool has not been seen as renewable from the view point of climate change mitigation. National greenhouse gas inventories under the United Nations Framework Convention on Climate Change (UNFCCC) should be prepared using methodologies given in IPCC Guidelines and good practice reports. Time series consistency is an important requirement. The IPCC guidelines do not give direct guidance how wood in peat should be treated - as renewable biomass fuel or as peat. The scientific considerations support treating the wood in peat as part of the peat (referred as Option 1 in this report). The wood in peat could also be considered in the inventory as other wood - a renewable biomass fuel (Option 2). Consistent time series for treatment of wood in peat would require recalculations in the inventory. In Option 1, the base year (1990) emissions would increase more than the current year emissions. In Option 2, the base year emissions would not change much, but current year emissions would be lowered. For both options, the impact of implementing the changes would be relatively small, the change in the total emissions in the Finnish inventory would be approximately 0.2% (0.1-1.0%) for Option 1 and 0.3% (0.1-1.4%) for Option 2. The impact on the total emissions was calculated assuming that the average share of wood in peat would apply also for peat extracted for combustion and that all wood in peat had been separated in the base year, and that currently all wood in peat is combusted as part of the peat. The share of wood in peat combusted has large regional differences, the methods used to estimate the share are uncertain, and also the data on the treatment of wood in peat in combustion is based on rough estimates. The range in the values reflects mainly regional differences, not the uncertainty of the nationwide average value. The IPCC good practice guidance report encourages recalculations that result in more accurate and complete estimates. It also encourages countries to peer review and validate the refinements before they are being implemented, especially if the base year will change as a result. Continuing the current practice (Option 3) has a relatively small impact on the total emissions and the emission trend. It overestimates current year emissions compared with the base year, and is therefore conservative. Recalculations using Option 1 or Option 2 would require improvements in the estimates on the wood content in peat combusted and wood separated from peat before combustion. Any recalculation should be reinforced with transparent reporting and documentation. Peat contains also decomposed or partly decomposed woody material which is mixed with the rest of the decomposed plant material which forms the peat. These wood-based components have been combusted with the rest of the peat and the treatment of emissions in the inventory has been consistent. Especially drained peatlands can contain a tree cover which is removed before the peat production begins. The treatment of the emissions from combustion of this woody material as renewable biomass has been consistent in the inventory. This report addresses only the treatment of the old, non-decomposed large woody pieces in peat, not the treatment of the other wood-based material described in the two above paragraphs.