Bioenergy Carbon Capture And Storage Research Articles

Energy and GHG emissions assessment for biochar-enhanced advanced biofuels value chains

Biochar has an enormous potential to store carbon in the long-term. Differently than BioEnergy Carbon Capture and Storage (BECCS) technologies, biochar incorporates biogenic carbon in a solid form that offers multiple benefits as carbon sink, soil improver or for advanced materials production. The present study proposes an innovative approach, where carbon sequestration through biochar is obtained through the integration of slow pyrolysis with fast pyrolysis in decentralised biorefining systems, and then converted producing drop-in fuels from pyrolysis oil hydrotreating or gasification and Fischer-Tropsch (FT) synthesis. The scope is either to achieve negative GHG emissions assigned to advanced biofuels, or to export the generated carbon credit for the carbon markets (i.e. outside the biofuels carbon intensity). The innovative concept entails process integration and optimisation for the different stages of biomass drying, conversion and upgrading into biofuels in a way to reduce fossil-based inputs, applying a full value chain approach. Methodological choices for the assumptions on life cycle emissions calculation are discussed, evaluating the environmental performances by comparing the new concept to traditional biofuels value chains. Using a tailored lifecycle accounting methodology, this paper demonstrates that high GHG emissions savings can be achieved. The improved scenario shows how the carbon sequestration with biochar further reduces the carbon intensity up to –4.2 gCO2e MJ−1 for pyrolysis oil-based fuels, and to −20.2 gCO2e MJ−1 for FT-based fuels: this demonstrated that carbon negative sustainable biofuels can be obtained. The study demonstrates that an integrated biorefinery of 100 MW capacity can deliver additional 13.3 and 6.8 ktons of CO2e of GHG savings of per year, from drop-in fuels made of hydrotreated pyrolysis oil and FT synthesis, respectively.

Optimizing high-dimensional forestry for wood production and carbon sinks

Our model for optimizing stand-level wood production and carbon sinks includes individual-tree models for forest growth, an advanced model for soil carbon, detailed wood production economy, and an intertemporal objective for the value of wood production and carbon sinks/emissions. Carbon stocks include aboveground biomass and carbon in forest soil and in wood products. Optimization of the management regime, rotations and thinning timing, and type and intensity are carried out by reinforcement learning. Including the social price of carbon causes a regime switch from continuous cover forestry to clear-cuts, postponed lighter thinning, and a longer rotation, and, with a high carbon price, to solutions with pure clear-cuts or solutions utilizing stands as pure carbon stocks. Carbon price has profound effects on stand values, and the bare land value may well exceed the value before a clear-cut. The total average carbon stock is maximized with harvest and a long rotation instead of "no harvesting". Bioenergy, carbon capture, and storage (BECCS) always increases the value of wood production but not necessarily the value of carbon sinks. With BECCS, increasing carbon stocks in trees and forest soil remains optimal.

The Case for Carbon Capture and Storage Technologies

In this paper, we use the literature to help us better understand carbon capture costs and how these estimates fare against those of avoided costs, focusing on bioenergy carbon capture and storage (BECCS), carbon capture and storage (CCS), as well as direct air capture technologies. We approach these questions from a meta-analysis perspective. The analysis uses meta-analysis tools while applying them to numerical rather than statistical studies. Our analysis shows that avoided costs are, on average, 17.4% higher than capture costs and that the carbon intensity of the feedstock matters: the estimates for coal-based electricity generation capture costs are statistically smaller than those for natural gas or air. From a policy perspective, the literature suggests that the costs of CCS are like the 45Q subsidy of USD 50 per metric ton of carbon captured.

A robust investment decision to deploy bioenergy carbon capture and storage—exploring the case of Stockholm Exergi

The upscaling of novel carbon dioxide removal, such as bioenergy carbon capture and storage (BECCS), to gigatonne scales is an urgent priority if global warming is to be limited to well below 2 °C. But political, economic, social, technological, environmental and regulatory uncertainty permeates BECCS projects and deters investors. To address this, we explore options to improve the robustness of BECCS deployment strategies in the face of multi-dimensional uncertainties. We apply Dynamic Adaptive Planning (DAP) through expert interviews and Robust Decision Making (RDM) through exploratory modelling, two decision making under deep uncertainty methods, to the case of Stockholm Exergi, an early mover aiming to deploy BECCS at a combined heat and power plant in the capital of Sweden. The main contributions of the research are to 1) illustrate how a quantification of robustness against uncertainty can support an investment decision to deploy BECCS 2) comprehensively cover uncertain vulnerabilities and opportunities of deploying BECCS, and 3) identify critical scenarios and adaptations to manage these uncertainties. The main conclusions are: investing in BECCS is relatively robust if assessing performance across many scenarios and if comparing the worst-cases of either investing, or not doing so. Not investing could miss out on up to € 3.8 billion in terms of net present value. The critical uncertainties of BECCS can be managed by strengthening biomass sustainability strategies and by gaining support for negative emission trading regulation on carbon markets, e.g., voluntary or Paris Agreement Article 6. Even in vulnerable scenarios of average electricity prices above 82 €/MWh, if trading regulation is implemented before 2030 and if negative emission prices exceed 151 €/CO2, investing in BECCS performs better than not doing so in 96% of cases. We suggest that facility-level parameters and cost-reductions are of little importance for BECCS investments and upscaling. It is regulatory certainty of operating revenues, e.g., through negative emission markets, that needs to be provided by policymakers.

Current technology landscape of biochar in carbon capture and storage research via bibliometric analysis

<abstract> <p>This study explores the current technology landscape and intersection of biochar and carbon capture and storage (CCS) within the engineering field, presenting a meticulous analysis gleaned from the Scopus database through bibliometric analysis. In response to the urgent need to address the escalating climate crisis, biochar, with its high carbon content, emerges as a promising and resilient tool for carbon sequestration. A literature review establishes biochar's pivotal role in mitigating climate change with contributions including substantial carbon sequestration potential, economic benefits, and positive impacts on soil structure and crop yields. Distinguishing between the applications of biochar and CCS, this paper emphasizes their complementary roles in decarbonization. By employing VOSviewer, an advanced bibliometric tool, a quantitative exploration of global connections identifying prominent authors, highly cited literature, and research trends is provided. The results reveal a substantial increase in publications related to biochar in CCS, particularly during the rapid development phase from 2016 to 2023, reflecting a growing interest in utilizing biochar as a carbon sink. Key insights from the co-occurrence analysis of keywords shed light on evolving research focuses, with three distinct clusters demonstrating the interconnectedness of adsorption, biochar, and pyrolysis. The precise method highlights a shift in research focus towards more impactful areas, particularly water pollutant removal and adsorption. The conclusion emphasizes biochar's dual role in soil carbon sequestration and carbon capture technologies, showcasing its versatility as a valuable tool in climate change mitigation efforts. Despite challenges in large-scale implementation, biochar, especially in the context of direct air capture and bioenergy CCS, emerges as a cost-effective and environmentally friendly adsorbent. In summary, this bibliometric analysis encapsulates a rigorous exploration of biochar and CCS, contributing valuable insights for researchers, policymakers and practitioners. By navigating uncharted territory, this study guides future endeavors toward impactful and relevant areas of study in the pursuit of sustainable climate change mitigation.</p> </abstract>

Life cycle optimisation for negative emission technologies in electricity generation

Negative emission technologies (NETs) have been identified as the key to achieve carbon dioxide (CO2) emission targets in most coutries. However, selecting the most appropriate and cost-efficient NET to meet these targets is challenging. Thus, a deeper understanding of the system impacts of NETs is necessary for effective decision-making. This work presents a life cycle optimisation (LCO) study of a set of NET technologies. LCO study combines life cycle analysis with techno-economic analysis to optimise and screen process alternatives such as bioenergy carbon capture and storage (BECCS), direct air carbon capture and storage (DACCCS), and biochar. The proposed methodology was demonstrated with a case study with five scenarios to achieve two objectives: to minimise total system cost and to minimise net CO2 emissions. The case study analysed different NET configurations to decarbonise an existing coal-fired power plant in East Malaysia (Sarawak). In this work, an existing Balingian Coal-Fired Power Plant was considered. NET configurations were assessed based on critical performance aspects such as total life cycle carbon emissions (TLCCE) and total life cycle cost input (TLCCI). However, it is worth emphasising that the proposed methodology can be revised to handle other NET configurations that were not explicitly addressed in this paper. This can be done by utilising relevant data and assumptions that are specific to each NET configuration. Results from the case study show that the minimum cost case provides an optimum NET configuration with TLCCE and TLCCI ranging from -0.02 kgCO2eq to 100.28 kgCO2eq and 23.99 USD/MWh to 1466.70 USD/MWh, respectively. In terms of life cycle analysis, DACCS shows a favourable TLCCI of 23.99 USD/MWh and TLCCE of -0.02 kgCO2eq/MWh. On the other hand, minimising CO2 emissions results in a 7% to 17% higher TLCCI in Scenario 2 and 3 but a similar trend in each sub-system can still be observed. This has proven that higher cost is required in the case when the CO2 emissions were to be minimised.

Sustainable aviation fuels – Options for negative emissions and high carbon efficiency

Mitigating the climate impact from aviation remains one of the tougher challenges in adapting society to fulfill stated climate targets. Long-range aviation cannot be electrified for the foreseeable future and the effects of combusting fuel at high altitude increase the climate impact compared to emissions of green-house gasses only, which further limits the range of sustainable fuel alternatives. We investigate seven different pathways for producing aviation biofuels coupled with either bio-energy carbon capture and storage (BECCS), or bio-energy carbon capture and utilization (BECCU). Both options allow for increased efficiency regarding utilization of feedstock carbon. Our analysis uses process-level carbon- and energy balances, with carbon efficiency, climate impact and levelized cost of production (LCOP) as primary performance indicators.The results show that CCS can achieve a negative carbon footprint for four out of the seven pathways, at a lower cost of GHG reduction than the base process option. Conversely, as a consequence of the electricity-intensive CO2 upgrading process, the CCU option shows less encouraging results with higher production costs, carbon footprints and costs of GHG reduction. Overall, pathways with large amounts of vented CO2, e.g., gasification of black liquor or bark, as well as fermentation of forest residues, reach a low GHG reduction cost for the CCS option. These are also pathways with a larger feedstock and corresponding production potential. Our results enable a differentiated comparison of the suitability of various alternatives for BECCS or BECCU in combination with aviation biofuel production. By quantifying the relative strengths and weaknesses of BECCS and BECCU and by highlighting cost, climate and carbon-efficient pathways, these results can be a source of support for both policymakers and the industry.

An overview of current trends in greenhouse gas reduction and possible strategies for their application in the oil and gas industry

This article provides an overview of the flare gases composition and methods for quantifying its emissions, as well as current trends in reducing greenhouse gas emissions in the oil and gas industry which are associated with the combustion of associated gas at flare installations. For the oil and gas industry, synergy strategies have been proposed with bioenergy carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS) technologies. Modern technologies for the use of associated gas without combustion at flare installations are considered. Proposals to reduce flare gas emissions in the conditions of the Far North and the Arctic are presented to ensure sustainable development. Keywords: flare gas; greenhouse gases; associated gas; oil and gas industry; sustainable development.

When burning wood to generate energy makes climate sense

ABSTRACT Over the last 20 years, IPPC reports have made it clear that the world must move beyond simply reducing the amount of carbon dioxide emitted into the atmosphere to actively removing it from the skies. (Solar and wind can reduce carbon emissions, but they do not remove greenhouse gases from the atmosphere). New BioEnergy Carbon Capture and Storage (BECCS) technologies have been emerging that can remove carbon dioxide emissions from the atmosphere and sequester them permanently underground. Indeed, many long-term scenarios for transitioning from today’s fossil fuel-dependent society to a future net zero society hinge on BECCS. But a key question is what bioenergy feedstock to use. In some cases, powering these facilities by burning biomass that comes from plantations in the US South is an option. Consequently, the study of the origins, production, and use of the fuel consumed by the world’s largest biomass-fired power plant in Drax, England, provides a useful case study of the potential advantages and disadvantages of the burning of biomass – wood pellets made from trees, bark, roots, stumps, millwaste, sawdust, and other woody vegetation – in place of fossil fuel to generate power for processes such as BECCS.

Integration of supply chain management of hybrid biomass power plant with carbon capture and storage operation

Bioenergy Carbon Capture and Storage (BECCS) is thought to be one of the most important technologies to realize the deep carbon emission reduction. An integrated model that combines biomass inventory management and carbon capture and storage (CCS) construction is built to analyze the operation management of BECCS plants. Biomass supply level and structure, operation costs, warehousing scale, and application restrictions are considered in the inventory management. The operation costs, learning effects, investment path, and capture efficiency of CCS are considered in the process of CCS construction. These two processes are integrated to maximize the total profit for biomass power plants under inter-temporal conditions. Jiangsu Province is selected for numerical simulation. The results show that the supply level of biomass has a great influence on the results, and the corresponding CCS technology needs to fully consider this factor for expansion. In addition, under strict carbon emission constraints, to avoid the high cost of CCS, policymakers are more inclined to achieve emission reduction targets by reducing power generation levels. Therefore, appropriate policy subsidies are needed to ensure the development of BECCS at this time.

Incentivizing BECCS—A Swedish Case Study

Negative carbon dioxide (CO2)-emissions are prevalent in most global emissions pathways that meet the Paris temperature targets and are a critical component for reaching net-zero emissions in Year 2050. However, economic incentives supporting commercialization and deployment of BioEnergy Carbon Capture and Storage (BECCS) are missing. This Policy and Practice Review discusses five different models for creating incentives and financing for BECCS, using Sweden as an example: (1) governmental guarantees for purchasing BECCS outcomes; (2) quota obligation on selected sectors to acquire BECCS outcomes; (3) allowing BECCS credits to compensate for hard-to-abate emissions within the EU ETS; (4) private entities for voluntary compensation; and (5) other states acting as buyers of BECCS outcomes to meet their mitigation targets under the Paris Agreement. We conclude that successful implementation of BECCS is likely to require a combination of several of the Policy Models, implemented in a sequential manner. The governmental guarantee model (Model 1) is likely to be required in the shorter term, so as to establish BECCS. Policy Models 2 and 3 may become more influential over time once BECCS has been established and accepted. Model 3 links BECCS to a large carbon-pricing regime with opportunities for cost-effectiveness and expanded financing. We conclude that Policy Models 4 and 5 are associated with high levels of uncertainty regarding the timing and volume of negative emissions that can be expected—Thus, they are unlikely to trigger BECCS implementation in the short term, although may have roles in the longer term. Based on this study, we recommend that policymakers carefully consider a policy sequencing approach that is predictable and sustainable over time, for which further analyses are required. It is not obvious how such sequencing can be arranged, as the capacities to implement the different Policy Models are vested in different organizations (national governments, EU, private firms). Furthermore, it is important that a BECCS policy is part of an integrated climate policy framework, in particular one that is in line with policies aimed at the mitigation of greenhouse gas (GHG) emissions and the creation of a circular economy. It will be important to ensure that BECCS and the associated biomass resource are not overexploited. A well-designed policy package should guarantee that BECCS is neither used to postpone the reduction of fossil fuel-based emissions nor overused in the short term as a niche business for “greenwashing” while not addressing fossil fuel emissions.

Achieving negative emissions through oceanic sequestration of vegetation carbon as Black Pellets

Natural processes and human activities produce vast amounts of dead vegetation which return CO2 to the atmosphere through decay and combustion. If such vegetation could be converted into biocoal and sequestered on the ocean floor, it could reduce the accumulation of atmospheric CO2 without involving sequestration in the form of CO2. Given that raw vegetation is unsuitable for large-scale energy applications, a process was developed to convert raw vegetation into a form of biocoal, termed Black Pellets, that solves the logistical and energy conversion problems of using raw vegetation for power generation. Seemingly overlooked is that properties of Black Pellets—higher density than seawater and resistance to microbial decay—may offer an environmentally safe way of sequestering vegetation carbon on the sea floor. Sequestering vegetation carbon by depositing biocoal as Black Pellets in the deep ocean (oceanic sequestration of biocoal—OSB) would be a means of achieving long-lasting negative emissions. Sacrificing the energy content of the deposited pellets would require substituting energy from other sources. If the substitute energy could be from lower-carbon natural gas or carbon-free sources, the effects would be less accumulation of atmospheric CO2 compared to using the pellets for energy and a nearly 60 to 100% reduction in the need for geologic sequestration compared to bioenergy carbon capture and storage (BECCS). If confirmed by research, OSB would be an addition to the sparse toolbox of negative emission technologies (NETs) which would give humankind more flexibility in meeting the goals of the Paris Agreement.

Supply Chain Driven Commercialisation of Bio Energy Carbon Capture and Storage

Pulp mills, as large biogenic CO2 point sources, could adopt Bio Energy Carbon Capture and Storage (BECCS) through retrofitting carbon capture. These existing carbon sources constitute a great potential to roll out BECCS on commercial scale. Yet, despite political targets for negative emission production in Sweden, no incentive schemes were thus far enacted. While previous proposals focus on governmental compensation, the aim of this work is to set BECCS into the supply chain of a wide array of consumer products and thereby find alternative or complementary, business-driven, ways to incentivise BECCS when applied to the pulp and paper industry. In this work, we assess a “value proposition” for low-carbon products in supply chains linked to the pulp and paper industry. By projecting the costs and negative emissions related to BECCS from the pulp mill to typical consumer products, as exemplified by three case study products, we show how BECCS can substantially reduce the carbon footprint of the consumer products, while only marginally increasing their cost. Additional price premiums could shorten the payback period of the initial investment in BECCS. The developed business case presents how actors along the supply chain for pulp and paper products can collectively contribute to securing financing and to mitigating investment risks. The results challenge the private sector, i.e., the companies along the pulp-and-paper supply chain to commit considerable investments also in the case without or with too weak direct political incentives. We conclude by discussing the governance implications on corporate and public level to enable the collaborative “bottom-up” adoption of BECCS.

Reuniting the Biogeochemistry of Algae for a Low-Carbon Circular Bioeconomy.

Given their advantages of high photosynthetic efficiency and non-competition with land-based crops, algae, that are carbon-hungry and sunlight-driven microbial factories, are a promising solution to resolve energy crisis, food security, and pollution problems. The ability to recycle nutrient and CO2 fixation from waste sources makes algae a valuable feedstock for biofuels, food and feeds, biochemicals, and biomaterials. Innovative technologies such as the bicarbonate-based integrated carbon capture and algae production system (BICCAPS), integrated algal bioenergy carbon capture and storage (BECCS), as well as ocean macroalgal afforestation (OMA), can be used to realize a low-carbon algal bioeconomy. We review how algae can be applied in the framework of integrated low-carbon circular bioeconomy models, focusing on sustainable biofuels, low-carbon feedstocks, carbon capture, and advances in algal biotechnology.

Ccs in the Pulp and Paper Industry – Implications on Regional Biomass Supply

The Swedish climate policy framework requires national GHG emissions to reach net zero by 2045 and become negative thereafter. Bioenergy carbon capture and storage (BECCS) has been identified as a possible main contributor to reach these targets by providing negative emissions – both to offset residual emissions in “hard-to-abate” sectors and to achieve 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 which could potentially be captured. This work investigates the biomass supply required for large scale implementation of BECCS in the pulp and paper industry. Regional biomass supply possibilities are evaluated by choosing four pulp and paper mills located in different parts of Sweden. The results show that regional biomass supply can limit the possibilities for BECCS implementation in regions with high competition for biomass. In regions with low competition and high availability of biomass regional biomass supply can potentially assist CCS implementation on biogenic sources. It is concluded that for a densely populated and industrialized region with high use of logging residues in the heating sector, in this work represented by southern Sweden where two of the studied mills are located, the possibility to increase regional supply of logging residues to fuel the capture process while maintaining mill production output, is limited due to competition for the same assortment of biomass from the energy sector (combined heat and power in district heating systems).

Detection and Quantification of CO <sub>2</sub> Seepage in Seawater Using the Stoichiometric Cseep Method: Results from a Recent Subsea CO <sub>2</sub> Release Experiment in the North Sea

Carbon Capture and Storage (CCS) is a potential significant mitigation strategy to combat climate change and ocean acidification in climate change scenarios e.g.,. Three out of four 1.5°C- consistent emission pathways published by the IPCC include CCS as well as bioenergy CCS (BECCS) as mitigation options. However, the scale of current CCS implementation is insufficient to affect the global climate, and thousands of large-scale CCS facilities need to be deployed by 2040 to meet mitigation targets. Moreover, the technology is in early stage of research, development, and demonstration e.g., and involves uncertainties and risks e.g.,. Currently, there are encouraging signals that CCS development and deployment are gaining momentum, and demonstration projects and experimental work are providing needed data for more thorough risk assessment.

Achieving Net Zero Emissions Requires the Knowledge and Skills of the Oil and Gas Industry

The challenge facing society in the 21st century is to improve the quality of life for all citizens in an egalitarian way, providing sufficient food, shelter, energy, and other resources for a healthy meaningful life, while at the same time decarbonizing anthropogenic activity to provide a safe global climate, limiting temperature rise to well-below 2°C with the aim of limiting the temperature increase to no more than 1.5°C. To do this, the world must achieve net zero greenhouse gas (GHG) emissions by 2050. Currently spreading wealth and health across the globe is dependent on growing the GDP of all countries, driven by the use of energy, which until recently has mostly been derived from fossil fuel. Recently, some countries have decoupled their GDP growth and greenhouse gas emissions through a rapid increase in low carbon energy generation. Considering the current level of energy consumption and projected implementation rates of low carbon energy production, a considerable quantity of fossil fuels is projected to be used to fill the gap, and to avoid emissions of GHG and close the gap between the 1.5°C carbon budget and projected emissions, carbon capture and storage (CCS) on an industrial scale will be required. In addition, the IPCC estimate that large-scale GHG removal from the atmosphere is required to limit warming to below 2°C using technologies such as Bioenergy CCS and direct carbon capture with CCS to achieve climate safety. In this paper, we estimate the amount of carbon dioxide that will have to be captured and stored, the storage volume, technology, and infrastructure required to achieve the energy consumption projections with net zero GHG emissions by 2050. We conclude that the oil and gas production industry alone has the geological and engineering expertise and global reach to find the geological storage structures and build the facilities, pipelines, and wells required. Here, we consider why and how oil and gas companies will need to morph from hydrocarbon production enterprises into net zero emission energy and carbon dioxide storage enterprises, decommission facilities only after CCS, and thus be economically sustainable businesses in the long term, by diversifying in and developing this new industry.

Machine learning exploration of the critical factors for CO2 adsorption capacity on porous carbon materials at different pressures

The growing environmental issues caused by CO2 emission accelerate the development of carbon capture and storage (CCS), especially bio-energy CCS as an environment-friendly and sustainable technique to capture CO2 using porous carbon materials (PCMs) produced from various biomass wastes. This study developed quantitative structure-property relationship models based on 6244 CO2 adsorption datasets of 155 PCMs to predict the CO2 adsorption capacity and analyze the relative significance of physicochemical properties. The results suggested that random forest (RF) models showed good accuracy and predictive performance based on physicochemical parameters of PCMs and adsorption conditions with the test dataset (R2 > 0.9). In general, textural properties were more crucial than chemical compositions of porous carbons to the change of CO2 adsorption capacity. At a low pressure (0.1 bar), the volumes of mesopore and micropore played an important role according to the RF analysis, but had a negative correlation with CO2 adsorption capacity based on the Pearson correlation coefficient (PCC) analysis. The relative importance of ultra-micropore increased along with the increase of pressure. The PCC value between ultra-micropore volume and CO2 uptake amount was up to 0.715 (p < 0.01) at 1 bar and 0 °C. The influence of chemical compositions was complex. The N content was confirmed to positively correlate to the CO2 adsorption capacity but its contribution was much lower than that of ultra-micropores. This study provided a new approach for fostering the rational design of porous carbons for CO2 capture via statistical analysis and machine learning method, which facilitated adsorbents screening for the cleaner production.

Can bioenergy carbon capture and storage aggravate global water crisis?

Bioenergy carbon capture and storage (BECCS) is an effective option for mitigation of greenhouse gas (GHG) emissions. Nevertheless, there is barely serious debate about whether its implementation can possibly jeopardize the global water resources security. Here, we provided an assessment of biomass-based Substitute Natural Gas (BioSNG) production combined with CCS, a promising BECCS technology, in terms of global water resources security, with a focus on the growth of two typical second-generation bioenergy crops: switchgrass and miscanthus. A bottom-up analysis approach was applied in this paper to calculating water consumption for BECCS and estimating water quality deterioration caused by increasing fertilizer and pesticide application. The results indicated that water usage of BECCS was equal to adding 12.86%–16.64% (switchgrass) and 17.59%–26.06% (miscanthus) additional water stress on global available water resources at 2100. Additional N fertilizer application in 2100 would be equal to over 84%, 55% and 42% for both switchgrass and miscanthus under three CCS capture efficiency scenarios, respectively, comparing to such global scale in 2012. Additional phosphate fertilizer adding to global annual available water at 2100 were 0.004–0.008 mg L−1 (switchgrass) and 0.003–0.006 mg L−1 (miscanthus), respectively. The secondary environmental hazards, such as N2O emission, would offset GHG emission mitigation by BECCS. Meanwhile, the enrichment and leaching of pesticide residues increased the risk of groundwater contamination. This study revealed water consumption and contamination issues caused by BECCS cannot be neglected. Thus, additional studies of accurate land-use models in global scale and advanced technology for biofuel extraction are needed in the future.

Potassium Ash Interactions with Oxygen Carriers Steel Converter Slag and Iron Mill Scale in Chemical-Looping Combustion of Biomass—Experimental Evaluation Using Model Compounds

Chemical-looping combustion (CLC) is a combustion technology in which a solid oxygen carrier is used to convert fuel. The oxygen carrier is oxidized in air and subsequently transferred to a separate reactor in which it reacts with the fuel. The produced CO2 is inherently separated from the air components, making CLC a promising technology for carbon capture and storage (CCS). CLC of biomass combined with CCS (bioenergy CCS; BECCS) is a way to generate negative CO2 emissions and thus interesting for climate change mitigation. Undesirable chemical reactions between ash and oxygen carriers are a challenge in BECCS because of the reactive nature of biomass ash. This article examines two low-cost steel industry byproducts that have shown desirable fuel conversion properties in CLC: iron mill scale (Glodskal B) and steel converter slag (LD-slag). Their interactions with potassium ash model compounds (KCl, K2CO3,K2SO4, and KH2PO4) in a reducing atmosphere have been investigated. Mixtures of oxygen carriers and potassium salt have been reduced for 6 h in CO and steam in a laboratory-scale fixed-bed reactor at 850 °C. The reduced samples have been analyzed with SEM/EDS and XRD. The reactivity of the mixtures during reduction and oxidation has also been examined by thermogravimetric analysis (TGA). K2CO3 increased the reaction rate for the reduction of Glodskal and inhibited the reactivity of LD-slag. KH2PO4 formed a K−P−Fe component with apparent low melting temperature with Glodskal, causing agglomeration, and decreased the reduction/oxidation rate in TGA. KH2PO4 formed a K−P−Ca component with apparent high melting temperature with LD-slag causing agglomeration but the reduction rate was not affected. The study suggests that the iron mill scale and LD-slag should not be rejected as oxygen carriers for CLC based on potassium ash interaction.