Biogenic CO2 Research Articles

High‐Resolution Lagrangian Inverse Modeling of CO2 Emissions Over the Paris Region During the First 2020 Lockdown Period

AbstractStringent mobility restrictions across the world during the COVID 19 pandemic have impacted local economies and, consequently, city carbon budgets, offering a unique opportunity to evaluate the capability of scientific approaches to quantify emissions changes. Our study aims to quantify and map CO2 emissions from fossil fuel and biogenic CO2 fluxes over the Paris metropolitan area during the first lockdown period (March‐May 2020) in France, in comparison with the same period in 2019. Our inversion system relies on transport model simulations initiated with the Weather Research and Forecasting chemistry transport model combined with a high‐resolution fossil fuel CO2 emissions inventory, and biogenic CO2 fluxes from a vegetation model. The inversion with atmospheric observations from a network of six towers resulted in a positive re‐adjustment of fossil fuel CO2 emissions in 2019 and 2020 compared to prior. In 2020, the inversion resulted in a large emission reduction (43%) compared to 2019, while the reductions were estimated to be 37% based on the prior inventory itself. By assimilating CO mixing ratios in addition to CO2, the traffic emission estimates were reduced by 68% in 2020, compared to nontraffic (29%). Various sensitivity tests show that prior emission uncertainty and different background conditions significantly impacted the emissions estimates. We conclude that our current inversion system with atmospheric CO2 monitoring makes it possible to identify the emission decrease in 2020 partly over the urban region. However, additional information on prior emission errors and a dense network will be needed to map emissions precisely.

Source Attribution of Atmospheric CO2 Using 14C and 13C as Tracers in Two Chinese Megacities During Winter

AbstractIdentifying the sources of atmospheric Carbon dioxide (CO2) is an important prerequisite for developing effective mitigation strategies. Here we conducted regular observations of the atmospheric CO2 mixing ratio and its carbon isotope compositions (i.e., Δ14C and δ13C) in Xi'an and Beijing during winter, to estimate source contributions of CO2 emissions in Chinese megacities. The results showed that CO2 emissions in both Xi'an and Beijing originated mainly from fossil‐fuel sources, which contributed 65 ± 3% and 82 ± 2% of the total CO2 enhancement, respectively, during the sampling period; the results also revealed a substantial biogenic CO2 contribution during winter. We further separated the fossil‐fuel sources into contributions from coal, oil and natural gas combustions. We found that coal combustion was the dominant anthropogenic source in Xi'an, accounting for 54 ± 4% of the total fossil‐fuel emissions, and oil and natural gas contribute almost equally to the emissions. In contrast, emission from natural‐gas combustion was the main fossil‐fuel source in Beijing, accounting for more than half of the total fossil‐fuel emissions, whereas, coal combustion contributed only 17 ± 10%. These top‐down results are generally consistent with emission inventory when seasonal variations of emissions are considered; some differences between the two methods indicated that the inventory for Xi'an might be underestimating the emissions from oil consumption. This pilot study confirms the potential of direct verification between top‐down and bottom‐up methods from the perspective of source attribution.

Process Analysis of Chemical Looping Gasification of Biomass for Fischer–Tropsch Crude Production with Net-Negative CO2 Emissions: Part 1

Large-scale biofuel production plants require an efficient gasification process that generates syngas of high quality (with minimal gas contaminants and inert gases) to minimize the extent of the syngas cleaning processes required for liquid biofuel production. This work presents process modeling of the chemical looping gasification (CLG) process for syngas production. The CLG process is integrated with a Fischer–Tropsch synthesis (FTS) process to produce Fischer–Tropsch (FT) crude with net-negative CO2 emissions, enabling process and system-level analyses of this novel biomass-to-liquid process. CLG resembles indirect gasification in an interconnected circulating fluidized bed reactor, where instead of inert bed material, a solid-oxygen carrier, such as mineral ores rich in iron or manganese oxides, is used. The oxygen carrier particles undergo oxidation and reduction in the air reactor and fuel reactor, respectively, thereby providing heat and oxygen for gasification. This work uses data from CLG experiments performed with steel converter slag as the oxygen carrier and investigates its potential when integrated with different downstream gas cleaning trains and the subsequent fuel synthesis process with the primary objective of quantifying and evaluating the performance of the integrated CLG–FT process plant. Syngas with a high energy content of 12 MJ/Nm3 (lower heating value basis) is predicted with a cold gas efficiency of 73%. CO2/CO ratios, higher than indirect biomass gasification, are also predicted in the raw syngas produced; thus, there exists an opportunity to capture biogenic CO2 with a relatively lower energy penalty in the subsequent gas cleaning stages. This work quantifies other key performance indicators, such as heat recovery potential, negative CO2 emission capacity, and FT crude production efficiency of the CLG–FT plant. A 100 MWth CLG plant produces roughly 677–696 barrels per day of FT crude, with net-negative emissions of roughly 180 kilotonnes of CO2 annually.

Carbon dioxide mineralization in recycled concrete aggregates can contribute immediately to carbon-neutrality

Bioenergy with carbon capture and storage (BECCS) is a carbon dioxide removal (CDR) solution necessary to achieve net-zero-carbon-emissions goals. While the BECCS potential from large industrial emitters has been quantified, the BECCS potential of small emitters, such as biogas facilities, has not been investigated. Moreover, most BECCS solutions rely on the expected availability of large geological storage capacity for future CDR implementation, although the deployment of CO2 transport and storage supply chains is still a barrier for geological carbon storage ambitions. An alternative opportunity for permanent sequestration of CO2 is concrete, in which captured CO2 can be permanently fixed through carbon dioxide mineralization technologies. We describe and discuss this solution by quantifying the potential of a European bioenergy with carbon capture, utilization, and storage (BECCUS) supply chain, which relies on biogenic CO2 from biogas facilities as a CO2 source, and on carbon dioxide mineralization in concrete as a permanent CO2 sink. This solution is available today, can be adopted seamlessly, and does not need economies of scale for its deployment. We find that European biogas facilities produce 24 Mtons of biogenic CO2 per year, of which 4 Mtons of CO2 per year are emitted from facilities already upgrading biogas into bio-methane. We estimate that carbon dioxide mineralization in recycled concrete aggregates in Europe could permanently store up to 8 Mtons of CO2 per year. Despite the limited storage potential, BECCUS supply chains would reduce CO2 transportation distance and system complexity compared to BECCS supply chains, and would result in a marketable product, namely concrete. Overall, carbon dioxide mineralization in recycled concrete aggregates combines carbon utilization with permanent sequestration, hence contributing to carbon-neutrality goals.

211 Greenhouse Gas Emissions from Two Beef Systems from Birth to Slaughter in Eastern Nebraska

Abstract Greenhouse gas emissions from a conventional (CONV) pasture-based cattle production system with cows wintered on corn residue and summer grazing of brome pasture was compared with partial-confinement system (ALT) with cows and calves in a drylot during the summer and grazed cover crops and corn residue over the fall and winter. Four groups of 20 cows were in each system. Eddy covariance methods were used to measure emissions from grazed areas (corn residue and pasture) and pen chambers were used to measure emissions from feedlot pens (cows and calves). Cattle from the CONV system produced more CH4 and CO2 but produced more beef per cow exposed (321 and 303 kg HCW for CONV and ALT, respectively). Measured CH4 and modeled N2O emissions totaled 7.5 ± 0.3 and 7.4 ± 0.3 kg CO2e kg-1 HCW for CONV and ALT production, respectively. There was a measured uptake of 233 g C m-2 and 98 g C m-2 from brome pasture and cover crop, respectively. Accounting for CH4 and N2O emissions using global warming potential (GWP) of 23 and 298 resulted in a net sink of 0.7 ± 0.2 kg CO2e kg-1 HCW for CONV and source of 16.7 ± 1.5 kg CO2e kg-1 HCW for ALT. The same calculation using global warming potential (GWP) of 4 and 234 resulted in a net sink of 10.9 ± 1.0 kg CO2e kg-1 HCW for CONV and source of 7.1 ± 1.5 kg CO2e kg-1 HCW for ALT. Carbon sequestration from perennial grasslands in the CONV was enough to offset all emissions and biogenic CO2 and the annual forage grazed in the ALT system offset 33 to 72% of systems emissions depending on GWP metric used.

Modelling synthetic methane production for decarbonising public transport buses: A techno-economic assessment of an integrated power-to-gas concept for urban biogas plants

The integration of power-to-gas (PtG) technology into existing urban anaerobic digestion (AD) plants could be an interesting concept to recycle biogenic CO2 and increase CH4 production as renewable fuel to further decarbonize public transport buses (PTB). However, such implementation is challenging for several reasons, including power restrictions during peak load, physical and temporal availability of CO2 from AD plants, and the need for expensive intermediate gas storages to avoid mismatch between the constrained synthetic CH4 production and the variable fuel demand. To investigate whether synthetic CH4 could be a feasible alternative for buses currently powered by fossil fuels, a dynamic model was built for discrete-event simulations of PtG technology integrated into an urban AD plant designed to supply biomethane as fuel for bus fleets. Different scenarios were assessed, including variations in power availability to run a proton exchange membrane electrolyser as well as variations in the production scale of synthetic CH4 based on ex-situ biological methanation. The results show that a constrained power utilization (maximum of 12 h per day) increased the production cost of synthetic CH4 by 20%. In contrast, an increase in PtG production capacity from 0.75 MWth to 2.25 MWth decreased costs by 16%. From the PTB operators’ perspective, the total cost of ownership (TCO) increased in all analysed scenarios when replacing diesel buses by gas buses powered by synthetic CH4. However, when using synthetic CH4 as drop-in fuel to replace natural gas in existing gas bus fleets, the TCO could be reduced up to 4.4% depending on the PtG plant configuration and the assumed fossil fuel price. Furthermore, our results show that a carbon tax on fossil fuels has only a limited effect on promoting synthetic CH4 as alternative fuel for PTB, and additional incentives should be put in place to prioritize a fuel switch, especially for existing gas bus fleets.

Managing food waste is key to tackling climate change

Managing food waste is key to tackling climate change

Economic and Environmental Potential of Large-Scale Renewable Synthetic Jet Fuel Production through Integration into a Biomass CHP Plant in Sweden

The potential of bio-electro-jet fuel (BEJF) production with integration into an existing biomass-based combined heat and power (CHP) facility was investigated. The BEJF is produced via Fischer–Tropsch (F–T) synthesis from biogenic CO2 and H2 obtained by water electrolysis. Techno-economic (TEA)- and life. cycle (LCA)- assessments were performed to evaluate the production cost and environmental impact of the BEJF production route. The BEJF mass fraction reached 40% of the total F–T crude produced. A reduction of 78% in heating demands was achieved through energy integration, leading to an increase in the thermal efficiency by up to 39%, based on the F–T crude. The total production cost of BEJF was in the range of EUR 1.6–2.5/liter (EUR 169–250/MWh). The GWP of the BEJF was estimated to be 19 g CO2-eq per MJ BEJF. The reduction potential in GWP in contrast to the fossil jet baseline fuel varied from 44% to more than 86%. The findings of this study underline the potential of BEJF as a resource-efficient, cost-effective, and environmentally benign alternative for the aviation sector. The outcome is expected to be applicable to different geographical locations or industrial networks when the identified influencing factors are met.

Does renewable mean good for climate? Biogenic carbon in climate impact assessments of biomass utilization

AbstractUsing biomass to substitute fossil resources is seen as one of the sustainable ways to tackle climate change. Yet not all biomass projects can be a priori declared beneficial. A climate impact assessment, such as life cycle assessment or carbon footprint, is crucial for a science‐based policy recommendation. However, those assessments can often be incomplete, especially since many of those adopt an assumption that biogenic CO2 emissions cause no harm to the climate and do not need to be accounted. Such a simplistic “neutrality assumption” can lead to inaccurate results and thus to undesired consequences. This article synthesizes and further develops the diverse argumentation against the “neutrality assumption,” especially regarding the complexity of biomass production, differences in the timing of emission, allocation procedure, and climate change characterization methodology. Thus, the article draws a broader picture of the complex issue of biomass projects and argues for more comprehensive assessments.

Carbon Footprint Assessment of a Novel Bio-Based Composite for Building Insulation

This research explores the carbon removal of a novel bio-insulation composite, here called MycoBamboo, based on the combination of bamboo particles and mycelium as binder. First, an attributional life cycle assessment (LCA) was performed to define the carbon footprint of a European bamboo plantation and a bio-insulation composite, as well as its ability to remove CO2 along its lifecycle at a laboratory scale. Secondly, the Global Worming Potential (GWP) was estimated through a dynamic LCA with selected end-of-life and technical replacement scenarios. Finally, a building wall application was analyzed to measure the carbon saving potential of the MycoBamboo when compared with alternative insulation materials applied as an exterior thermal insulation composite system. The results demonstrate that despite the negative GWP values of the biogenic CO2, the final Net-GWP was positive. The technical replacement scenarios had an influence on the final Net-GWP values, and a longer storage period is preferred to more frequent insulation substitution. The type of energy source and the deactivation phase play important roles in the mitigation of climate change. Therefore, to make the MycoBamboo competitive as an insulation system at the industrial scale, it is fundamental to identify alternative low-energy deactivation modes and shift all energy-intensity activities during the production phase to renewable energy.

The carbon footprint balance of a real-case wine fermentation CO2 capture and utilization strategy

The wine industry is extremely vulnerable to climate change given the impact of temperature, water or soil conditions on wine production. Transformation strategies toward more sustainable models would help the industry to overcome the weak points. The present study evaluates the environmental impact of the so-called CO2-alcoholic fermentation processes (CO2-AFP) strategy, a recently developed eco-innovative strategy, which offers a new pathway toward a greener wine-making production with a 16.79% reduction of the carbon footprint considering scopes 1 (direct emissions), 2 (emissions generated directly in the production of electricity), and 3 (indirect emissions embodied in the organization's value chain). This strategy is based on a novel Carbon Dioxide Utilization approach from a biogenic CO2 released by fermentation processes to produce a fully marketable and environmentally friendly chemical product at a global level, i.e., sodium carbonate.This paper presents the strategy development corresponding to a real case: a medium-size winery and distillery in Spain, where the “CO2-AFP Strategy” has been successfully tested and scaled-up. Detailed and tested carbon capture and utilization schemes are used to evaluate the overall carbon footprint balance (carbon calculation, capture potential, and carbon balance) via an improved hybrid multiregional input-output-lifecycle assessment model (MRIO-LCA). The benefits go beyond the reduction of carbon footprint in the fermentation industry. The application of the “CO2-AFP Strategy” implies a revolution, in terms of Circular Economy, in the sodium carbonate industry, as the symbiotic process between the different stages of the value chain will allow downstream carbon footprint reductions, facilitating a greener sodium carbonate production.

Quantification of Urban Forest and Grassland Carbon Fluxes Using Field Measurements and a Satellite‐Based Model in Washington DC/Baltimore Area

AbstractCities are taking the lead on climate change mitigation with ambitious goals to reduce carbon dioxide (CO2) emissions. The implementation of effective mitigation policies will require accurate measurements to guide policy decisions and monitor their efficacy. Here, we present a comprehensive CO2inventory of an urban temperate forest and unmanaged grassland using field observations. We estimate the annual storage of CO2by vegetation and soils and place our biogenic flux estimates in the context of local fossil fuel (FF) emissions to determine when, where, and by how much biogenic fluxes alter net CO2flux dynamics. We compare our hourly estimates of biogenic fluxes in the forest site to modeled estimates using a modified version of Urban‐Vegetation Photosynthesis and Respiration Model (Urban‐VPRM) in Washington DC/Baltimore area presenting the first urban evaluation of this model. We estimate that vegetation results in a net biogenic uptake of −2.62 ± 1.9 Mg C ha−1 yr−1in the forest site. FF emissions, however, drive patterns in the net flux resulting in the region being a net source of CO2on daily and annual timescales. In the summer afternoons, however, the net flux is dominated by the uptake of CO2by vegetation. The Urban‐VPRM closely approximates hourly forest inventory based estimates of gross ecosystem exchange but overestimates ecosystem respiration in the dormant season by 40%. Our study highlights the importance of including seasonal dynamics in biogenic CO2fluxes when planning and testing the efficacy of CO2emission reduction polices and development of monitoring programs.

Biogas Plants as Hydrogen Production Facilities and Greenhouse Gas Sinks: Technology Comparison, Challenges and Potentials for Carbon Negative Hydrogen Production (HyBECCS)

The biological transformation of industrial value creation aims to provide solutions with regard to the ecological challenges of our time. Concerning climate change, the most critical transformation area is the energy sector. Alternatives to fossil energy supply as well as the active removal of carbon dioxide (CO2) from the atmosphere are considered the most important challenges that technology must provide solutions for. A promising approach in this context is the carbon-negative hydrogen production from biogenic sources (HyBECCS). This approach can be implemented on the basis of existing biogas plants. Technology alternatives for retrofitting these plants to HyBECCS facilities are elaborated and their respective strengths, weaknesses, opportunities and threats are derived in this paper. Further, taking the example of Baden-Wuerttemberg in Germany, the ecologic potentials concerning hydrogen (H2) production and greenhouse gas (GHG) reduction are estimated. The current total H2 demand of 1.8 TWh/a in this area could be fully covered if 1/7 to 1/4 of existing biogas plants were retrofitted for H2 production. The substitution of gray H2 can avoid GHG emissions of 2.2-3.7 million t CO2 per year. In addition, capture and storage or long-term use of the resulting biogenic CO2 can enable negative emissions of 2.5-6 million t CO2 per year.

Large-Scale Implementation of Bioenergy With Carbon Capture and Storage in the Swedish Pulp and Paper Industry Involving Biomass Supply at the Regional Level

Bioenergy with carbon capture and storage (BECCS) has been identified as a possible major contributor to efforts to reach ambitious climate targets through the provision of negative emissions–offsetting residual fossil emissions in “hard-to-abate” sectors and accomplishing net-negative emissions. The pulp and paper industry is the single largest consumer of biomass in Sweden, with many large point sources of biogenic CO2 emissions that could be captured. This work investigates the biomass supply required for large-scale implementation of BECCS in the pulp and paper industry. Logging residues are considered as a fuel to supply the additional energy demand imposed by the capture plant, and the potential of these residues is evaluated in a case study that includes four pulp and paper mills located in regions of Sweden with different conditions for biomass supply. Two of the mills are located in southern Sweden, where there is strong competition for logging residues from the heating sector, and two of the mills are located in northern Sweden, where the competition is weaker. We show that implementing carbon capture at the four pulp and paper mills using regional logging residues to supply the additional heat demand required by the capture process (the reboiler heat demand) has the potential to capture around 4.6 Mt CO2/year. The results also show that the fuel share of the capture cost, i.e., the cost to supply the reboiler heat demand with regional logging residues, is 22–30 €/tCO2 captured, where the lower value corresponds to regions with weaker competition for logging residues (in this study, northern Sweden). In regions that have competition for logging residues, the possibility to increase the regional supply of logging residues to fuel the capture process while maintaining mill production output is limited, which in turn limits the possibilities to generate negative emissions via BECCS. In contrast, in regions with a low level of competition and strong availability of logging residues, there is an additional potential for logging residues to cover the additional heat demand required for CCS implementation.

Technological Demonstration and Life Cycle Assessment of a Negative Emission Value Chain in the Swiss Concrete Sector

Switzerland, such as most of the other countries which are part of the Paris agreement, decided to reduce GHG emissions to zero by 2050. The ambition of net-zero GHG emission across all industrial sectors can only be achieved by rapid decarbonization and the deployment of negative emission technologies to compensate residual emissions from for example agriculture. In the scope of this work, the proof of technology of a negative emission value chain at industrial scale in the concrete sector is presented. The core of the system is a mineralization technology, which fixes biogenic CO2 permanently as calcium carbonate in concrete aggregate. In addition, the net-negativity in terms of GHG emissions and environmental burdens beyond these are quantified in a Life Cycle Assessment (LCA). It could be shown that an industrial-scale mineral carbonation process can be seamlessly integrated in today's concrete recycling processes and that it can process relevant amounts of concrete aggregate while storing on average 7.2 kg CO2 per ton of concrete aggregate. Moreover, material tests revealed that the carbonated concrete aggregate fulfills the same service as the regular one—thus no significant effects on the concrete properties could be observed. The LCA shows that every processing step requires materials and energy, and thus generates associated emissions. However, from a cradle to gate perspective, the carbon removal efficiency is 93.6%. Thus, 1,000 kg of CO2 stored generate 64 kg of CO2-eq. emissions. Furthermore, it could be shown that biogas upgrading can supply sufficient amounts of CO2 until 2030 in Switzerland. From 2030 on, more and more CO2 from other emission sources, such as waste incineration, need to be utilized to exploit the full potential of the value chain, which is going to be 560 kt of negative CO2 emissions in Switzerland in 2050, corresponding to 30% of the projected demand within the national borders.

Environmental assessment of amending the Amager Bakke incineration plant in Copenhagen with carbon capture and storage.

Amending municipal solid waste incineration with carbon capture and storage (CCS) is a new approach that can reduce the climate change impacts of waste incineration. This study provides a detailed analysis of the consequences of amending the new Amager Bakke incinerator in Copenhagen (capacity: 600,000 tonnes waste per year) with CCS as a post-combustion technology. Emphasis is on the changes in the energy flows and outputs as well as the environmental performance of the plant; the latter is assessed by life cycle assessment. Amending Amager Bakke with CCS of the chosen configuration reduces the electricity output by 50% due to steam use by the capture unit, but introducing post-capture flue gas condensation increases the heat output utilized in the Copenhagen district heating system by 20%. Thus, the overall net energy efficiency is not affected. The CCS amendment reduces the fossil CO2 emissions to 40 kg CO2 per tonne of incinerated waste and stores 530 kg biogenic CO2 per tonne of incinerated waste. Potential developments in the composition of the residual waste incinerated or in the energy systems that Amager Bakke interacts with, do not question the benefits of the CCS amendment. In terms of climate change impacts, considering different waste composition and energy system scenarios, introducing CCS reduces in average the impact of Amager Bakke by 850 kg CO2-equivalents per tonne of incinerated waste. CCS increases the environmental impacts in other categories, but not in the same order of magnitude as the savings introduced within climate change.

On the embodied carbon of structural timber versus steel, and the influence of LCA methodology

Reducing greenhouse gas emissions in the built environment is key to mitigating climate change. This paper uses Life Cycle Assessment (LCA) to explore whether glue-laminated timber (glulam) has a significantly lower whole-life embodied carbon (Global Warming Potential; GWP) than functionally-equivalent structural steel. Alongside a baseline assessment that follows standard practice, a variety of further sensitivity analyses establish how differing assumptions affect results. Assessment found that the GWPs were highly dependent on: (1) the assumed end-of-life scenarios; (2) the approach used to consider biogenic CO2, and; (3) whether the timing of emissions was considered. In general, glulam had the lowest GWP when incinerated (with energy recovery) at end-of-life. However, when recycling is modelled according to current standards, glulam GWPs were in amongst those of steel, giving no clear ranking of materials. Landfilled glulam had a lower GWP than steel if some biogenic carbon was assumed to be permanently stored. That may be appropriate given recent guidance from the Intergovernmental Panel on Climate Change, but is not allowed in the updated standards for LCA of construction products (e.g. EN 15804:2019). Six additional impact categories were also assessed to give a broader environmental comparison. The relative impact of the two materials depended on the impact category assessed, with glulam generally having a similar or lower impact than steel. Given the findings of this paper, further research on end-of-life treatment and LCA methodology is critical to ensure that strategies aiming to reduce GWP by material selection are effective in practice.

Valorization of secondary feedstocks from the agroindustry by selective catalytic oxidation to formic and acetic acid using the OxFA process

The selective oxidative conversion of seven representative fully characterized biomasses recovered as secondary feedstocks from the agroindustry is reported. The reaction system, known as the “OxFA process,” involves a homogeneous polyoxometalate catalyst (H8PV5Mo7O40), gaseous oxygen, p-toluene sulfonic acid, and water as solvent. It took place at 20 bar and 90 °C and transformed agro-industrial wastes, such as coffee husks, cocoa husks, palm rachis, fiber and nuts, sugarcane bagasse, and rice husks into biogenic formic acid, acetic acid, and CO2 as sole products. Even though all samples were transformed; remarkably, the reaction obtains up to 64, and 55% combined yield of formic and acetic acid for coffee and cocoa husks as raw material within 24 h, respectively. In addition to the role of the catalysts and additive for promoting the reaction, the influence of biomass components (hemicellulose, cellulose and lignin) into biogenic formic acid formation has been also demonstrated. Thus, these results are of major interest for the application of novel oxidation techniques under real recovered biomass for producing value-added products.Graphical abstract

Environmental Product Declarations of Structural Wood: A Review of Impacts and Potential Pitfalls for Practice

The use of wood and timber products in the construction of buildings is repeatedly pointed towards as a mean for lowering the environmental footprint. With several countries preparing regulation for life cycle assessment of buildings, practitioners from industry will presumably look to the pool of data on wood products found in environmental product declarations (EPDs). However, the EPDs may vary broadly in terms of reporting and results. This study provides a comprehensive review of 81 third-party verified EN 15804 EPDs of cross laminated timber (CLT), glulam, laminated veneer lumber (LVL) and timber. The 81 EPDs represent 86 different products and 152 different product scenarios. The EPDs mainly represent European production, but also North America and Australia/New Zealand productions are represented. Reported global warming potential (GWP) from the EPDs vary within each of the investigated product categories, due to density of the products and the end-of-life scenarios applied. Median results per kg of product, excluding the biogenic CO2, are found at 0.26, 0.24, and 0.17 kg CO2e for CLT, glulam, and timber, respectively. Results further showed that the correlation between GWP and other impact categories is limited. Analysis of the inherent data uncertainty showed to add up to ±41% to reported impacts when assessed with an uncertainty method from the literature. However, in some of the average EPDs, even larger uncertainties of up to 90% for GWP are reported. Life cycle assessment practitioners can use the median values from this study as generic data in their assessments of buildings. To make the EPDs easier to use for practitioners, a more detailed coordination between EPD programs and their product category rules is recommended, as well as digitalization of EPD data.

Assessment of urban CO2 budget: Anthropogenic and biogenic inputs

Understanding combinations of biogenic and anthropogenic inputs, and dynamics of carbon dioxide (CO2) fluxes in the urban environment is critical to investigate feedback between carbon cycle and climate system. The main objectives of this study are to analyse the role and interactions of anthropogenic and biogenic CO2 emission sources and sinks in the total carbon cycle within city limits, determine processes controlling urban ecosystem-atmosphere gas exchange under varying environmental conditions with a high temporal and spatial resolution.The research addressing this issue was carried out in Wroclaw, the fourth largest city in Poland, throughout the year from July 2017 to August 2018. Chamber measurements of surface-atmosphere CO2 and CO2 net fluxes across various types of land cover (grassland, city park and arable land) provided the basis for assessing biogenic component of the urban C budget. In particular, the approach applied Picarro CRDS (cavity ring-down spectroscopy) technique with model G2201-I. Anthropogenic C fluxes were reported based on local statistical datasets and existing emission inventories, as well as the Low Emission Economy Plan from the Wroclaw urban area.The findings showed that biogenic fluxes, over the course of one year, accounted for about 16.3% (RESP = 0.68 Mton CO2·yr−1) of the total city carbon emissions for Wroclaw, being entirely compensated by local vegetation C uptake (GEE = −0.89 Mt. CO2·yr−1). Compared to fluxes given by the previously reported emission inventory, the net biogenic CO2 sink (NEE) of 0.201 Mt. CO2·yr−1 was substantially greater, which indicates that the biosphere in Wroclaw is a net biogenic C sink. The average annual C budget in Wroclaw, obtained from the investigation of sectoral emission trends including those related to energy, road traffic, industrial processes, and other fluxes (human respiration), reaches about 3.87 kg C·m−2·yr−1.