Greenhouse Gas Mitigation Potential Research Articles

Exploring Corn Cob Gasification as a Low-Carbon Technology in the Corn Flour Industry in Mexico

In 2021, Mexico produced approximately 24.2 million tons of white corn, generating 3.6 million tons of corn cob residue. The final disposal of corn cob poses an environmental challenge in certain regions. This study examines the technical–economic feasibility and the greenhouse gas (GHG) mitigation potential of integrating a small-scale cogenerating gasifier fueled by corn cob into a nixtamalized corn flour manufacturing small and medium-sized enterprise (SME). This integration enables the generation of heat and electricity from the produced synthesis gas. Moreover, the process yields residual carbon, which can be used as biochar for soil restoration and removing atmospheric CO2. This option holds significance for the corn flour agroindustry in Mexico, as, in 2021, it consumed approximately 601.9 GWh of electrical energy and 938,279 GJ of thermal energy from LP Gas in its manufacturing processes to produce 2.6 million tons of nixtamalized white corn flour. These processes contributed to a total emission of 410,232 tons of CO2 into the atmosphere. The findings of this study demonstrate a cumulative reduction of 51.7% in CO2 emissions, resulting in economic benefits of USD 85,401 in 2017 for a case study SME that annually produces 1039 tons of corn flour. This study reveals the integration of a gasifier–cogenerator system fueled by corn cob as an economically viable low-carbon technology in the corn flour manufacturing industry.

Greenhouse gas mitigation and soil carbon stabilization potential of forest biochar varied with biochar type and characteristics

Biochar is increasingly used in climate-smart agriculture, yet its impact on greenhouse gas (GHG) emissions and soil carbon (C) sequestration remains poorly understood. This study examined biochar-mediated changes in soil properties and their contribution to C stabilization and GHG mitigation by evaluating four types of biochar. Soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions, soil chemical and biological properties, and soil organic carbon (SOC) mineralization kinetics were monitored using greenhouse, laboratory, and modeling experiments. Three pine wood biochars pyrolyzed at 460 °C (PB-460), 500 °C (PB-500), 700 °C (PB-700), and one pine bark biochar from gasification at 760 °C (GB-760) were added into soil at 1 % w/w basis. Soils amended with biochar were used to cultivate sorghum for three months in a greenhouse, followed by three months of laboratory incubation. Data obtained from laboratory incubation was modeled using various statistical approaches. The PB-500 and PB-700 reduced cumulative N2O-N emissions by 68.5 % and 73.9 % and CO2 equivalent C emissions by 66.9 % and 72.4 %, respectively, compared to unamended control. The N2O emissions were positively associated with soil nitrate N, available P, and biochar ash content while negatively associated with SOC. The CO2 emission was negatively related to biochar C:N ratio and volatile matter content. Biochar amended soils had 49.2 % (PB-500) to 87.7 % (PB-700) greater SOC and 22.9 % (PB-700) to 48.1 % (GB-760) greater sorghum yield than the control. While PB-700 had more saprophytes than the control, the GB-760 yielded a greater yield than biochars prepared by pyrolysis. Microbial biomass C was 7.23 to 23.3 % greater in biochar amended soils than in control. The double exponential decay model best explained the dynamics of C mineralization, which was associated with initial soil nitrate N and available P positively and total fungi and protozoa biomass negatively. Biochar amendment could be a climate smart agricultural strategy. Pyrolysis pine wood biochar showed the greatest potential to reduce GHG emissions and enhance SOC storage and stability, and gasification biochar contributed more to SOC storage and increased crop yield.

Overlooked in-situ sulfur disproportionation fuels dissimilatory nitrate reduction to ammonium in sulfur-based system: Novel insight of nitrogen recovery

Sulfur-based denitrification is a promising technology in treatments of nitrate-contaminated wastewaters. However, due to weak bioavailability and electron-donating capability of elemental sulfur, its sulfur-to-nitrate ratio has long been low, limiting the support for dissimilatory nitrate reduction to ammonium (DNRA) process. Using a long-term sulfur-packed reactor, we demonstrate here for the first time that DNRA in sulfur-based system is not negligible, but rather contributes a remarkable 40.5 %–61.1 % of the total nitrate biotransformation for ammonium production. Through combination of kinetic experiments, electron flow analysis, 16S rRNA amplicon, and microbial network succession, we unveil a cryptic in-situ sulfur disproportionation (SDP) process which significantly facilitates DNRA via enhancing mass transfer and multiplying 86.7–210.9 % of bioavailable electrons. Metagenome assembly and single-copy gene phylogenetic analysis elucidate the abundant genomes, including uc_VadinHA17, PHOS-HE36, JALNZU01, Thiobacillus, and Rubrivivax, harboring complete genes for ammonification. Notably, a unique group of self-SDP-coupled DNRA microorganism was identified. This study unravels a previously concealed fate of DNRA, which highlights the tremendous potential for ammonium recovery and greenhouse gas mitigation. Discovery of a new coupling between nitrogen and sulfur cycles underscores great revision needs of sulfur-driven denitrification technology.

EXHAUST GAS ANALYSIS OF DIESEL - CADOBA FARINOSA FORSKK BIO-ETHANOL BLENDED FUEL SAMPLES RUNNING ON COMPRESSION IGNITION ENGINE

The world is facing declining liquid fuel reserves at a time when energy demand is exploding. As the supply decreases and costs rise, everyone will be forced to adopt the alternative energy resources. In order to achieve a secure and stable energy supply that does not cause environmental damage, renewable energy sources must be explored and promising technologies should be developed. This study investigates the effects of exhaust gases of diesel-Cadoba farinosa forskk bio-ethanol blended fuel samples run on a compression ignition engine. The test fuels were prepared; BDE2 (97% Diesel and 2% bio-ethanol volumetric proportion), BDE4, BDE6, BDE8 and BDE10 with 1% biodiesel (palm oil methyl esters) was maintained throughout to prevent phase separation of the ethanol and diesel respectively. The engine performance and exhaust gas analysis were also conducted to investigate the effect of bio-ethanol as diesel fuel extender, with a TD110-115 single-cylinder, four-stroke and air-cooled, compression ignition engine test rig, under different loading conditions, and incorporated with an SV-5Q automobile exhaust gas analyzer was used to monitor and measure the concentration of gaseous emissions, such as; exhaust gas temperature (EGT), carbon dioxide (CO 2), carbon monoxide (CO), and unburned hydrocarbon (HC) from the engine tail pipe. Results of the test revealed an appreciable increase in exhaust gas temperature of 16.66% due to the rise in cylinder pressure and temperature respectively. An appreciable decrease in HC, CO and CO 2 15.7%, 37.5% and 15% respectively emissions was recorded for all blended fuel samples with the exception of diesel. While, the least CO and CO 2 emission levels were observed for BDE10 fuel samples. On the account of its satisfactory engine performance behavior, fuel conservation advantages, and inherent greenhouse gas mitigation potentials, the candidacy of Cadoba Farinosa Forskk bio-ethanol and diesel blends, offers the promise of a prospective fuel for compression ignition engines.

A multi-scale framework for advancing national dairy sector GHG mitigation in Israel

Dairy production systems display a wide range of greenhouse gas (GHG) emission characteristics influenced by factors like geographical location, farm size, herd composition, milk yield, management practices, and existing infrastructure.Effective national GHG mitigation plans for the dairy industry should incorporate strategies that account for the diversity within this system. This paper aims to introduce a multi-scale framework to assess the GHG mitigation potential within the Israeli dairy system. It begins by analyzing the GHG intensity per unit of milk produced by a representative sample of 145 farms (20 % of the national dairy farms). It then extrapolates the data to the regional and national scales. The research reveals an average carbon footprint of 1.18 (ranging from 0.8 to 1.64) kg CO2e per kilogram of milk (FPCM) over the life cycle up to the farm gate. Upon scaling up, the study estimates the annual carbon footprint of the Israeli dairy industry at 1,777,800 t of CO2e. Consequently, this framework highlights areas with significant GHG emissions that require attention and opportunities for national mitigation based on the detailed characteristics of the studied systems.

'Climate Healing Stones': Common Minerals Offer Substantial Climate Change Mitigation Potential.

This review proposes that mineral-based greenhouse gas (GHG) mitigation could be developed into a substantial climate change abatement tool. This proposal was evaluated via three objectives: (1) synthesise literature studies documenting the effectiveness of geological minerals at mitigating GHG emissions; (2) quantify, via meta-analysis, GHG magnitudes that could be abated by minerals factoring-in the carbon footprint of the approach; and (3) estimate the global availability of relevant minerals. Several minerals have been effectively harnessed across multiple sectors-including agriculture, waste management and coal mining-to mitigate carbon dioxide/CO2 (e.g., olivine), methane/CH4 (e.g., allophane, gypsum) and nitrous oxide/N2O (e.g., vermiculite) emissions. High surface area minerals offer substantial promise to protect soil carbon, albeit their potential impact here is difficult to quantify. Although mineral-based N2O reduction strategies can achieve gross emission reduction, their application generates a net carbon emission due to prohibitively large mineral quantities needed. By contrast, mineral-based technologies could abate ~9% and 11% of global CO2 and CH4 anthropogenic emissions, respectively. These estimates conservatively only consider options which offer additional benefits to climate change mitigation (e.g., nutrient supply to agricultural landscapes, and safety controls in landfill operations). This multi-benefit aspect is important due to the reluctance to invest in stand-alone GHG mitigation technologies. Minerals that exhibit high GHG mitigation potential are globally abundant. However, their application towards a dedicated global GHG mitigation initiative would entail significant escalation of their current production rates. A detailed cost-benefit analysis and environmental and social footprint assessment is needed to ascertain the strategy's scale-up potential.

Carbon storage and sequestration in a eucalyptus productive zone in the Brazilian Cerrado, using the Ca-Markov/Random Forest and InVEST models

Tropical ecosystems in Brazil, particularly Mato Grosso do Sul, possess substantial greenhouse gas (GHG) mitigation potential through carbon sequestration in tree forests. However, the expansion of agricultural activities poses a threat to this potential. Notably, eucalyptus forests could enhance carbon sequestration and reduce GHG emissions. This study focused on Três Lagoas, known as Brazil's cellulose capital, and aimed to evaluate carbon stock and sequestration for 2030 under business as usual (BAU) and protected forest (PF) scenarios. Combining Cellular Automata (CA) and Random Forest models implemented in Patch-Generating Land Use Simulation (PLUS) and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, we simulated land use scenarios and assessed ecosystem services generated by carbon sequestration. The results showed that the PF scenario indicated a higher total carbon stock than the BAU scenario, with a difference of 2.48 Tg. Carbon sequestration varied by period and scenario. Between 2010 and 2020, 3.88 Tg of carbon were sequestered. However, in the next period (2020–2030), the BAU scenario estimated 2.45 Tg in total carbon sequestration. In contrast, the PF scenario predicted 4.93 Tg of carbon sequestration for 2020–2030, surpassing the previous decade. Monetarily, carbon sequestration in 2010–2020 amounted to $92.48 million, decreasing to $58.49 million for 2020–2030 in the BAU scenario. In the PF scenario, sequestration for 2020–2030 increased to $ 117.43 million, nearly double that of the BAU scenario. In conclusion, combining the Ca-Markov/Random Forest and InVEST models revealed the spatiotemporal dynamics of carbon stock and sequestration in the municipality with the largest eucalyptus-planted area in Brazil. The results underscore the significant variability in carbon stocks and sequestration based on classes, periods, and scenarios analyzed. This study contributes valuable insights into the potential for carbon mitigation in this critical region.

Mid-season drain severity impacts on rice yields, greenhouse gas emissions and heavy metal uptake in grain: evidence from on-farm studies

Context or ProblemFlooded rice systems produce an important staple crop but are a source of methane (CH4) and arsenic (As) exposure. Introducing non-continuous flooding events can decrease seasonal CH4 emissions and grain As concentration. A single mid-season drain (MD: a 7-to 10-day soil drying period during the mid-season) is easier for farmers to manage than multiple drain events (e.g. alternate wetting and drying). Previous research has shown that a MD can accomplish these goals without yield reduction. However, depending on soils and precipitation, the soil drying severity during a MD can vary substantially. Objective or Research QuestionThe objectives of this study were to compare a MD to the farmer practice under on-farm conditions with respect to yields, greenhouse gas (GHG) emissions and As and cadmium (Cd – which can increase with non-continuous flooding). Second, to quantify the relationship between soil drying severity during the MD and the reduction in CH4 emissions and grain As. MethodsA three-year study with seven on-farm trials was implemented. Each trial had two treatments: a MD and the farmer practice. Grain yields, GHG emissions, and grain As and Cd concentrations were quantified for each treatment. ResultsGrain yields were similar between treatments. The MD decreased seasonal CH4 emissions by 20–77% (average of 52%), with the magnitude of reduction being related to soil-drying severity during the MD. Combining previous on-station data with this on-farm data, indicates that for every 1% reduction in soil gravimetric water content (GWC), seasonal CH4 emissions were reduced by 2.5% (r2 = 0.47). With MD, N2O emissions increased (average = 0.25 kg N2O-N ha−1), but accounted for only 3% of the global warming potential. The MD decreased grain As concentration (by 20% on average, but not related to soil drying severity), and there was no effect on grain Cd concentrations. ConclusionsGiven these results, an MD has similar GHG mitigation potential to other non-continuous flooding practices that require more drain periods and may be more difficult to implement. These results indicate that a MD is a viable on-farm management practice for GHG mitigation and reducing grain As concentration with limited risk of yield reduction. Implications or SignificanceThis is the first research that has documented the relationship between soil drying severity and reduction in CH4 emissions across soils. This relationship is a potentially useful tool for on-farm monitoring, but will need to be developed further across more locations.

Development of a framework to assess the greenhouse gas mitigation potential from the adoption of low-carbon road vehicles in a hydrocarbon-rich region

This study developed a novel assessment framework to analyze long-term energy transition in the road transport sector in which various technology options, market shares, policy measures, costs, and greenhouse gas emissions are considered in a single framework analysis. A data-intensive model was developed with the Low Emissions Analysis Platform (LEAP) and used to analyze policy scenarios up to 2050 for Alberta, Canada, a hydrocarbon-rich province with an emission-intensive energy sector. Three key policy measures – carbon pricing, zero-emission vehicle sales mandate, and incentivization – were analyzed in nine individual and combined policy scenarios. The transition to both hydrogen fuel cell electric vehicles and battery electric vehicles was assessed for all vehicle categories. Each fuel's full energy supply chain was modelled, including resource extraction, conversion, transmission and distribution, and fuelling, allowing for final and primary energy analysis. The findings show that carbon price and zero-emission vehicle incentives do not effectively lower greenhouse gas emissions on their own; zero-emission vehicle mandates are needed to transition the sector to a low-carbon energy system. The system-wide greenhouse gas emission footprints of hydrogen and battery electric vehicles are significantly below conventional vehicles in all cases. Scenarios biased towards battery electric vehicles had the most favorable results. The greenhouse gas emission footprint of hydrogen vehicles supplied by auto-thermal reforming with 91% carbon capture was lower than for battery electric vehicles powered by a primarily natural gas-based power grid. The findings on the effectiveness of carbon prices, incentives, and vehicle mandates should be considered by government policymakers aiming to reduce greenhouse gas emissions, infrastructure planners, and other energy stakeholders.

The Pathway to NDC and Carbon Neutrality: Roles of Optimum Degree between Marginal Abatement Cost and Social Cost of Carbon in the Thai Power and Industrial Sector

Thailand has formulated its climate change policy and updated the relevant plans and policies to align with the goal of achieving carbon neutrality and net-zero greenhouse gas (GHG) emissions. This study investigated the optimal level of GHG mitigation in Thailand by taking into account the marginal abatement cost (MAC) and social cost of carbon (SCC). The research also evaluated how energy efficiency and renewable energy technologies could influence GHG reduction in the power and industrial sectors and illustrate policy recommendations that could be aligned with the 2020–2050 policy and plan period. The findings indicated that there could be instances where GHG mitigation potential would be insufficient to reach the national milestone. In such cases, it would become imperative to leverage all technologies within the marginal abatement cost curve (MACC) and also utilize the SCC for policy decision-making and meeting the desired goals. In certain scenarios, the adoption of additional technologies or measures would be necessary, such as flexible power generation and deploying carbon capture and storage or hydrogen, which are high-cost technologies. Furthermore, preparations should be made for multiple levels of climate change policies and plans beyond 2030.

Deploying green hydrogen to decarbonize China’s coal chemical sector

China’s coal chemical sector uses coal as both a fuel and feedstock and its increasing greenhouse gas (GHG) emissions are hard to abate by electrification alone. Here we explore the GHG mitigation potential and costs for onsite deployment of green H2 and O2 in China’s coal chemical sector, using a life-cycle assessment and techno-economic analyses. We estimate that China’s coal chemical production resulted in GHG emissions of 1.1 gigaton CO2 equivalent (GtCO2eq) in 2020, equal to 9% of national emissions. We project GHG emissions from China’s coal chemical production in 2030 to be 1.3 GtCO2eq, ~50% of which can be reduced by using solar or wind power-based electrolytic H2 and O2 to replace coal-based H2 and air separation-based O2 at a cost of 10 or 153 Chinese Yuan (CNY)/tCO2eq, respectively. We suggest that provincial regions determine whether to use solar or wind power for water electrolysis based on lowest cost options, which collectively reduce 53% of the 2030 baseline GHG emissions at a cost of 9 CNY/tCO2eq. Inner Mongolia, Shaanxi, Ningxia, and Xinjiang collectively account for 52% of total GHG mitigation with net cost reductions. These regions are well suited for pilot policies to advance demonstration projects.

A comprehensive analysis of small-scale building integrated photovoltaic system for residential buildings: Techno-economic benefits and greenhouse gas mitigation potential

The present paper aims to highlight the techno-economic and greenhouse mitigation potential of the small-scale building integrated photovoltaic (BIPV) of 10 kW suitable for residential as well as small commercial agglomerations. To carry out this investigation a mathematical model has been developed utilizing the RetScreen simulation tool. The model has been implemented by choosing various cities across India that are major residential hubs such as Delhi, Lucknow, Indore, Jodhpur, Pune, and Coimbatore. The result showed that the energy production remained highest at Jodhpur i.e. 15678 kWh amounting to Rs. 94107/year of energy savings. The energy payback period (ENPP) for a 10 kW system has been obtained between 6 and 7 years. The highest capacity utilization factor (CUF) was obtained during March but the performance ratio (PR) and efficiency remained highest during December–January (Winter). Jodhpur had the highest net present value (NPV) and profitability index (PI) which indicated that Jodhpur was the most lucrative site among all locations. The simple and the equity payback (SPP and EPP) obtained were between 7.1 and 9.3 years. The Levelized cost of electricity (LCOE) was between Rs. 5.81/kWh- Rs. 6.95/kWh. The result also revealed that the 10 kW BIPV system was capable of reducing 15 tonnes/year of carbon and more than 400 tonnes of carbon in 25 years. The carbon credit earned by a single installation was more than Rs. 70 thousand in a year. If the current model is applied to 3000 households in a locality, there can be 40–50 GWh of energy savings amounting to Rs. 230–280 million.

Assessment of greenhouse gas mitigation from rice cultivation using alternate wetting and drying and rice straw biochar in Thailand

The mitigation of greenhouse gas (GHG) emissions and water usage optimization in rice cultivation is challenging for many agricultural countries, including Thailand, who have set goals of reaching net zero emissions and coping with droughts caused by climate change. Alternate wetting and drying (AWD) and biochar application are possible practices for achieving cleaner rice production through reduction of GHG emissions and water consumption. However, these methods’ potential varies by site, especially in areas with limited control of water levels. This study assessed the effects of AWD at different drying levels (10, 15, and 20 cm below the soil surface) and rice straw biochar on GHG emissions, yield production, water use, soil characteristics, and economic aspects. This study was conducted over two rice cultivation seasons: a major season in 2022 and a second season in 2023 at a field in Kalasin Province, northeastern Thailand. Using AWD and biochar reduced annual GHG emissions by 48.2% and 8.01%, respectively. Deeper drying levels of AWD showed greater mitigation potential than shallow levels. The combination of AWD and biochar had additional potential for GHG mitigation, however, this impact did not show statistical change as compared to their separate potentials. The adoption of AWD and biochar could also maintain the amount of rice yield compared to traditional practice. All levels of AWD saved irrigation water consumption by an average of 16.8% per season; the highest potential was observed in AWD at 10 cm below the soil surface. Biochar improved soil health after two seasons by enhancing soil pH and organic carbon sequestration. The combination of AWD and biochar did not additionally augment the capacity in water saving of AWD or soil improvement of biochar. The AWD water regime also did not increase net profits, while biochar decreased net profits due to the required investment in biochar production. Using AWD is a feasible way to mitigate GHG emissions and save water without affecting rice productivity and net profits in northeastern Thailand.

Livestock greenhouse gas emission and mitigation potential in China

Livestock is an important source of greenhouse gas emissions (GHGE) in China. Understanding the greenhouse gas (GHG) emission trends and reduction strategies in livestock is crucial for promoting low-carbon transformation of the livestock sector (LS) and achieving the goal of “carbon peak and carbon neutralization”. First, based on the life cycle assessment and IPCC coefficient methods, we calculated the GHGE of the LS in 31 provinces of China from 2000 to 2020 and identified the temporal and spatial evolution of GHG emission intensity. The LMDI method was then used to analyze the influence of efficiency, structure, economy, and population size on GHGE. Finally, the STIRPAT model was used to simulate the future evolution trend of the LS emissions under the SSPs scenario. The results revealed that the GHGE in the life cycle of livestock production decreased from 535.47 Mt carbon dioxide equivalent (CO2e) in 2000 to 532.18 Mt CO2e in 2020, and the main source was CH4 emissions from enteric fermentation of livestock. Economic and efficiency factors markedly influenced the changes in GHGE from the LS in China. Further, economic factors contributed >40% to the increase in GHGE in most provinces. Under the SSP1, SSP2, and SSP4 scenarios, livestock production can achieve the carbon peak target in 2030. Under the baseline scenario (SSP2), the GHGE of China's LS in 2030 and 2060 are expected to be 491.48 Mt CO2e and 352.11 Mt CO2e, respectively. The focus of mitigation measures for livestock production in the future is to optimize the production structure of the LS, promote the low-carbon transformation of the energy structure of livestock feeding, and establish an efficient and intensive management model. In addition, we focus on emission reduction in key areas, such as Northeast and Northwest China, while optimizing diet and reducing food waste from the consumer side.

Nitrogen nutrient supply and greenhouse gas mitigation potentials from cover crops across Chinese croplands

Cover crops can benefit agricultural systems greatly by improving soil fertility, increasing soil organic carbon (SOC) contents, and promoting grain yield. Recently cover crops have been recommended as a practice to ameliorate croplands and develop nature-based climate solutions. However, the information as to where is potentially suitable for developing cover crops is lacking. Here, we try to map the potential regions suitable for cover crops and to estimate nitrogen nutrient supply and greenhouse gas (GHG) mitigation potentials with the hypothesis that all the suitable fallow lands are used for cover crops. First, we generated a smoothed normalized difference vegetation index (NDVI) series by Savitzky-Golay method from 2019 to 2021. Then, we produced the phenology dates and tracked the regular crop fallow periods in the three years. Next, we extracted the potential regions for cover crops based on the effective accumulated temperature requirements and drainage limit. Finally, we estimated nitrogen supply and GHG mitigation potentials using the previous measurements. Results show that nearly 13.3% (∼26.7 Mha) of current croplands can be planted with cover crops, providing 1.21 ± 0.26 Tg N yr−1 of nitrogen fertilizer. The potential cover crops can mitigate 58.85 ± 9.95 Tg CO2-eq yr−1 of GHG emissions. SOC sequestration is the dominant process in the GHG mitigation with a rate of 48.15 ± 5.34 Tg CO2-eq yr−1, equal to 30.1% ± 3.4% of the current annual total SOC sequestration in Chinese croplands. The study demonstrates an advanced framework in mapping the potential croplands available for cover crops and providing evidence-based planning of extending cover crops across China. The framework can be widely applied to other regions, contributing to building climate smart agriculture and developing nature-based climate solutions.

CO2, CH4, and N2O emissions from dredged material exposed to drying and zeolite addition under field and laboratory conditions

Dredging, the removal of sediment from water courses, is generally conducted to maintain their navigability and to improve water quality. Recent studies indicate that dredging can significantly reduce aquatic greenhouse gas (GHG) emissions. These studies, however, do not consider the potential emission from the dredged material (sludge) in the depot. In addition, it is unknown if and how GHG emissions from sludge depots can be reduced. Here we present spatiotemporal variations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes, as well as environmental variables from a sludge depot located in the Netherlands. Measurements were conducted monthly from the time the depot was filled until the sludge was dry and the depot was abolished. We also experimentally assessed the GHG mitigation potential of 1) keeping the sludge permanently inundated, and 2) the addition of different amounts of zeolite to increase sludge nitrogen binding capacity to reduce N2O emissions. In the depot and in the laboratory, a decrease in moisture content coincided with increased CO2 and N2O emissions while CH4 emissions decreased. We observed that permanent inundation reduced emissions (∼4 times less CO2-eq than in drying sludge). Adding zeolite lowered N2O fluxes from permanently inundated sludge but did not reduce total GHG emissions. During the depot's operational period, average CO2, CH4, and N2O fluxes were 5078, 27, and 5 mg m−2 d−1, respectively. GHG emissions from drying sludge occurred mainly in the form of CO2 (73% of the total CO2-eq emissions), with average GHG emission rates comparable to those reported for ditches and ponds. We estimate that approximately 14 tons of CO2-eq were emitted from the 0.011 km2 depot, which contained ∼20,000 m3 of sludge, during its entire operational period, and we argue that more studies are needed, considering different sludge origins, to expand our understanding of sludge depots.

Land use/land cover change-induced greenhouse gas emissions in the global biosphere reserve of tropical Afromontane forest

Land use/land cover (LULC) change is a prominent problem and source of greenhouse gas (GHG) emissions in tropical forests. However, little to no evidence is available on the contribution of biosphere reserves to reversing LULC change trajectories and reducing GHG emissions, particularly in tropical Afromontane forests. The objective of this study was to quantify the LULC change-induced GHG emissions from 1999 to 2020 in tropical Afromontane forests that were designated the Sheka Forest Biosphere Reserve (SFBR) by the MAB program of UNESCO in 2012. The IPCC Tier 1 approach was used to estimate GHG emissions. The results showed that the aggregated GHG emissions were 0.4 tonnes of CO2e ha−1 yr−1 in 1999, while they climbed to 1.46 tonnes of CO2e ha−1 yr−1 in 2010 and 5.2 tonnes of CO2e ha−1 yr−1 in 2020. Deforestation and forest degradation, the expansion of cropland, the development of tea plantations, settlement expansion, and the forest degradation of wetlands contributed to increased emissions by 40.4%, 32.2%, 17.6%, 8.3%, and 1.5% in 2010 and by 60%, 20%, 5.2%, 14.4%, and 0.33% in 2020, respectively. As a result, compared to 9.03 tonnes of CO2e ha−1 yr−1 in 1999, the overall GHG mitigation potential of the SFBR decreased by 12.6% in 2010 and 40.2% in 2020. The findings suggest that the SFBR's capacity to reduce GHG emissions was neither enhanced nor maintained by its designation as a forest biosphere reserve. Therefore, regularly monitoring the effectiveness of interventions and reconciling conflicting land use priorities would be essential for maintaining Afromontane forests and reducing GHG emissions. Promoting tree planting, afforestation, reforestation, and restoring degraded forest landscapes would play a vital role to minimize GHG emissions and enhance the mitigation potential of the ecosystem.

Impact of biochar amendments on soil water and plant uptake dynamics under different cropping systems

AbstractApplication of biochar amendments in agricultural systems has received much attention in recent years. In this study, we assess the 5‐year impacts of biochar application on soil water and plant interactions for an irrigated fresh market tomato (Solanum lycopersicum) and a rainfed pasture (Poaceae) cropping system. In particular, we focus on three varieties of locally produced biochar from agricultural waste materials—almond shell, walnut shell, and almond pruning residues that are pyrolyzed using a mobile pyrolysis unit. We used the soil hydrological model HYDRUS‐1D to explicitly track seasonal and annual soil water fluxes through changes in water retention, drainage, evaporation, and plant water uptake under biochar application. Modeling results show that the application of biochar at 5% increased soil water availability within the top 20 cm for a rainfed system, irrespective of biochar amendment type. This is clearly indicative of higher plant water uptake and greater water use efficiency (WUE) under biochar application. In contrast, a similar biochar amendment for the irrigated system did not affect WUE, instead reducing seasonal soil evaporation loss and thereby reducing irrigation demand. In both cropping systems, year‐to‐year variability in precipitation significantly impacted the total amount of water saved under biochar application with certain amendments retaining more water than others. Given that biochar application increased water retention irrespective of cropping systems, we further used a simple approach to determine yield trade‐off, if any, between control and biochar treatments. Our economic balance clearly demonstrates that the water saved by amending soil with biochar does not offset the yield disparity if compensated with carbon credits and therefore, application of biochar should be actively considered for both its direct and indirect benefits to potential greenhouse gas mitigation (e.g., diverting orchard waste from open burning), water savings, and soil health.

Supply chain system for a centralized biorefinery system based on switchgrass grown on marginal land in Michigan

AbstractThe feedstock supply chain of a biorefinery is critical in determining the economic and environmental performance of biofuels. This study investigated various feedstock supply chains for a centralized biorefinery based on different objective functions and how the biorefinery responds to supply chain volatility. For the analysis, a hypothetical centralized biorefinery was supplied by switchgrass grown on marginal lands in Michigan. From an economic standpoint, the minimum biofuel selling price is an important metric of the objective function, and the greenhouse gas mitigation potential is a similarly important metric for global warming impact. A trade‐off therefore exists between the economic and environmental performance of biofuels under this system configuration. However, when a carbon tax credit is applied to soil organic carbon sequestration in switchgrass production, the metric of the objective function may not be the key factor in establishing a supply chain as long as it is associated with biorefinery capacity as well as economic or environmental values. Year‐to‐year fluctuations in cellulosic biomass yield (supply chain volatility) might also prevent the biorefinery from operating at full capacity. Cellulosic biomass pellets can serve as an auxiliary feedstock for the centralized cellulosic biorefinery system to minimize the impacts of supply chain volatility.

Technoeconomic analysis of a fungal pretreatment-based cellulosic ethanol production

Cellulosic biomass shows great potential as feedstock for bioethanol production. Despite clear benefits in terms of greenhouse gas mitigation and bioproduct potential, the commercial production of cellulosic ethanol remains economically challenging at the current state of technology. This paper presents a technoeconomic analysis of a fungal pretreatment-based cellulosic ethanol plant with a processing capacity of 2000 tonnes of switchgrass per day. The production process model was designed and simulated using SuperPro Designer. The plant's ethanol yield, capital investment per unit capacity, and unit ethanol production cost were estimated to be 211.90 L/t of switchgrass, $ 3.60/L, and $ 1.44/L of ethanol, respectively. Fungal pretreatment was the major contributor (72%) to the total capital investment, mainly due to the large quantity of equipment required in the process. A positive net present value (NPV) was generated for the baseline model at ethanol selling price of $ 1.50/L, which increased by 5-fold for 80% glucose yield. Glucose yield was the most sensitive to NPV for all the process parameters evaluated.