The present investigation, carried out as a case study in a typical major city situated in a European coal combustion region (Krakow, Poland), aims at quantifying the impact on the urban air quality of residential heating by coal combustion in comparison with other potential pollution sources such as power plants, industry, and traffic. Emissions were measured for 20 major sources, including small stoves and boilers, and the particulate matter (PM) was analyzed for 52 individual compounds together with outdoor and indoor PM10 collected during typical winter pollution episodes. The data were analyzed using chemical mass balance modeling (CMB) and constrained positive matrix factorization (CMF) yielding source apportionments for PM10, B(a)P, and other regulated air pollutants namely Cd, Ni, As, and Pb. The results are potentially very useful for planning abatement strategies in all areas of the world, where coal combustion in small appliances is significant. During the studied pollution episodes in Krakow, European air quality limits were exceeded with up to a factor 8 for PM10 and up to a factor 200 for B(a)P. The levels of these air pollutants were accompanied by high concentrations of azaarenes, known markers for inefficient coal combustion. The major culprit for the extreme pollution levels was demonstrated to be residential heating by coal combustion in small stoves and boilers (>50% for PM10 and >90% B(a)P), whereas road transport (<10% for PM10 and <3% for B(a)P), and industry (4-15% for PM10 and <6% for B(a)P) played a lesser role. The indoor PM10 and B(a)P concentrations were at high levels similar to those of outdoor concentrations and were found to have the same sources as outdoors. The inorganic secondary aerosol component of PM10 amounted to around 30%, which for a large part may be attributed to the industrial emission of the precursors SO2 and NOx.

The European Union (EU) relies largely on bioenergy to achieve its climate and energy targets for 2020\ud and beyond. Special focus is placed on utilization of biomass residues, which are considered to cause low\ud environmental impacts.\ud We used the dataset from the latest European Commission document on the sustainability of solid and\ud gaseous biomass (SWD2014 259), complementing those results by: i) designing three pathways for\ud domestic-heat production using forest logging residues, with different combustion technologies; ii)\ud expanding the analysis to include forest carbon stock development with and without bioenergy; iii)\ud using absolute climate metrics to assess the surface temperature response by the end of the century to a\ud bioenergy and a reference fossil system; iv) including multiple climate forcers (well-mixed GHG, near\ud term climate forcers and surface albedo change); iv) quantifying life cycle impacts on acidification,\ud particulate matter emissions and photochemical ozone formation; v) reviewing potential risks for forest\ud ecosystem degradation due to increased removal of residues.\ud Supply-chain GHG savings of the three pathways analysed ranged between 80% and 96% compared to a\ud natural gas system, above the 70% threshold suggested by the EU. However, the climate impact of bioenergy\ud should be assessed by considering also the non-bioenergy uses of the biomass and by including\ud all climate forcers.\ud We calculate the Surface Temperature Response to bioenergy and fossil systems by means of Absolute\ud Global surface Temperature Potential (AGTP) metric. Domestic heating from logging residues is generally\ud beneficial to mitigate the surface temperature increase by 2100 compared to the use of natural gas and\ud other fossil sources. As long as residues with a decay rate in the forest higher than 2.7%*yr1 are\ud considered as feedstock, investing now in the mobilization of residues for heat production can reduce the\ud temperature increase by 2100 compared to all the fossil sources analysed, both in case of bioenergy as a\ud systemic change or in case of bioenergy as a transitory option.\ud Furthermore, several environmental risks are associated with the removal and use of forest logging\ud residues for bioenergy. These issues concern mostly local air pollution, biodiversity loss and, mainly for\ud stumps removal, physical damage to forest soils.\ud Forest logging residues are not free of environmental risks. Actions promoting their use should\ud consider: (i) that climate change mitigation depends mainly on the decay rate of biomass under natural\ud decomposition and time and rate of technology deployment, (ii) whether management guidelines aimed\ud at protecting long-term forest productivity are in place and (iii) whether proper actions for the management\ud of adverse effects on local air pollution are in place

The European Union relies largely on bioenergy to achieve its climate and energy targets for 2020 and beyond. We assess, using Attributional Life Cycle Assessment (A-LCA), the climate change mitigation potential of three bioenergy power plants fuelled by residual biomass compared to a fossil system based on the European power generation mix. We study forest residues, cereal straws and cattle slurry. Our A-LCA methodology includes: i) supply chains and biogenic-CO2 flows; ii) explicit treatment of time of emissions; iii) instantaneous and time-integrated climate metrics. Power generation from cereal straws and cattle slurry can provide significant global warming mitigation by 2100 compared to current European electricity mix in all of the conditions considered. The mitigation potential of forest residues depends on the decay rate considered. Power generation from forest logging residues is an effective mitigation solution compared to the current EU mix only in conditions of decay rates above 5.2% a−1. Even with faster-decomposing feedstocks, bioenergy temporarily causes a STR(i) and STR(c) higher than the fossil system. The mitigation potential of bioenergy technologies is overestimated when biogenic-CO2 flows are excluded. Results based solely on supply-chain emissions can only be interpreted as an estimation of the long-term (>100 years) mitigation potential of bioenergy systems interrupted at the end of the lifetime of the plant and whose carbon stock is allowed to accumulate back. Strategies for bioenergy deployment should take into account possible increases in global warming rate and possible temporary increases in temperature anomaly as well as of cumulative radiative forcing