Biomass Input Research Articles

Soil carbon storage capacity of drylands under altered fire regimes

The determinants of fire-driven changes in soil organic carbon (SOC) across broad environmental gradients remains unclear, especially in global drylands. Here we combined datasets and field sampling of fire-manipulation experiments to evaluate where and why fire changes SOC and compared our statistical model to simulations from ecosystem models. Drier ecosystems experienced larger relative changes in SOC than humid ecosystems—in some cases exceeding losses from plant biomass pools—primarily explained by high fire-driven declines in tree biomass inputs in dry ecosystems. Many ecosystem models underestimated the SOC changes in drier ecosystems. Upscaling our statistical model predicted that soils in savannah–grassland regions may have gained 0.64 PgC due to net-declines in burned area over the past approximately two decades. Consequently, ongoing declines in fire frequencies have probably created an extensive carbon sink in the soils of global drylands that may have been underestimated by ecosystem models.

Fast pyrolysis simulation via kinetic approach and multivariate analysis to assess the effect of biomass properties on product yields, properties, and pyrolyzer performance

Fast pyrolysis (FP) is the thermochemical conversion of biomasses and other carbonaceous materials into bio-oil (liquid), char (solid), and gas products to be used to generate heat, power, chemicals, and fuels of lower greenhouse gas emissions. Considering biomass properties highly affect the FP performance, this work used simulation and multivariate analysis tools to assess the effect of the composition of nine Brazilian biomasses on the FP energy demands, product yields, and bio-oil properties. A simulation, representing a pyrolyzer (480 °C, 1-s residence time), product recovery, and char combustion to meet FP energy demands, was built in Aspen Plus v.10 and validated against experimental data. A dataset correlating biomass compositions from 60 sources and FP outputs was obtained and analyzed, via two statistical methods, to detect similarities between feedstocks and correlate biomass inputs and process outputs. Hierarchical cluster analysis (HCA) separated the feedstocks into two main clusters: agricultural and woody biomasses. The main differences were associated with agricultural feedstocks having higher biomass H/C ratios, lower carbon and volatiles contents, and being of the CHL type (cellulose > hemicellulose > lignin), resulting in lower char and higher gas yields. As for correlations between inputs and outputs, HCA and principal component analysis (PCA) divided the parameters into five main groups: (i) biomass O/C ratio and cellulose content; (ii) bio-oil yield, heating value, and extractives content; (iii) biomass H/C ratio, hemicellulose content, and bio-oil quality metrics; (iv) ash content, char yield, and pyrolyzer heat duty; and (v) biomass lignin, volatiles, and heating value with gas yield and heating value. Several anticorrelations were also detected (e.g., bio-oil yield anticorrelated to bio-oil properties; char yield anticorrelated to gas yield). This work hopes to serve as a simplified roadmap for relationships between biomass properties and FP performance, providing guidelines for biomass selection for different bio-oil downstream applications and perspectives on future works on FP simulation.

Recalcitrant organic carbon plays a key role in soil carbon sequestration along a long-term vegetation succession on the Loess Plateau

Vegetation restoration effectively promotes soil quality and enhances soil organic carbon (SOC) sequestration. However, the dynamics and driving factors of SOC fractions during long-term vegetation succession remain unclear. In this study, a complete ∼ 160 years successional chronosequence from farmland to climax forest was used to study the dynamics and driving factors of SOC fractions in topsoil (0–20 cm) and subsoil (20–40 cm). The results showed that vegetation succession age significantly affected the SOC and its fractions (p < 0.05). The content of SOC fractions increased with succession age, especially recalcitrant organic carbon (ROC), which accounted for 62%–85% of the total SOC. Long-term vegetation succession enhanced the stability of SOC pools, reduced the proportion of active C, and facilitated the fixation of C. ROC was the best indicator of SOC accumulation within the entire profile. When vegetation succession reached the pioneer forest stage (∼110 years), the SOC content and fractions increased significantly (p < 0.05) owing to continuous plant biomass inputs. Moreover, soil C sequestration was controlled by total nitrogen content in the topsoil and by belowground biomass in the subsoil. This study indicates that long-term vegetation succession can effectively improve SOC accumulation and SOC pool quality, emphasizing the need to focus on SOC pool stabilization mechanisms under future climate change.

Temporal and Spatial Changes in Soil Organic Carbon in a Semi-Arid Area of Aohan County, Chifeng City, China

Soil organic carbon (SOC) plays a crucial role in arid zones, while land-use change could lead to changes in the balance of SOC. Therefore, the aim of this study was to determine the impact of land-use change on the temporal and spatial variability in SOC at the county scale. A semi-arid zone (Aohan County, Northeast China) covering a surface of 3800 km2 was selected for this study. SOC data for 65 and 182 soil samples from 1985 and 2021, respectively, were collected for major land-use types (forestland, farmland, grassland, and sandy land) across Aohan County to a depth of 20 cm. The impacts of different land-use types and land-use changes on SOC were evaluated. The results showed that land-use change enhanced the spatial variability in SOC over the last 36 years. The mean SOC in 2021 (7.49 g kg−1) was significantly higher than that in 1985 (6.91 g kg−1). Converting sandy land into grassland and farmland into forest or grassland would lead to significant accumulation of SOC, while the depletion of SOC occurred after grassland afforestation. The balance between aboveground biomass inputs and SOC decomposition was the determining reason that affected the accumulation of SOC. Vegetation restoration due to land-use change could alter both soil texture and the C/N ratio and could have positive effects on ecosystem recovery.

Preliminary Results of Innovative Two-Stage Torrefaction Technology Applied for Thermochemical Treatment of Sunflower Husk

This article proposes an innovative two-stage technology for biomass torrefaction generating high-quality biochar, more specifically biocoal, as solid fuel, and offering a promising solution to the challenges posed by the combustion of biomass. In particular, the higher quality of biochar as solid fuel reduces the build-up of unmanageable deposits on fired surfaces, as these deposits inhibit heat transfer and reduce the efficiency of biomass boilers. The proposed two-stage technology involves torrefaction in a hearth-type reactor at temperatures up to 250 °C, followed by a subsequent stage of cooling achieved through washing with water. The two-stage torrefaction technology is integrated within a vertical hearth reactor vessel composed of three superimposed trays serving for biomass input, torrefaction, and water washing combined with biomass cooling, respectively. Upon contact with torrefied biomass, cooling water turned into water vapor; hence, eliminating the requirement for subsequent biomass separation and drying. The system was tested on sunflower husk, and results showed a reduction in the content of problematic elements such as alkali metal chlorides or sulfur compounds in biochar ash, suggesting lower corrosion rates of convective heating surfaces of the boiler under ash sediments. It is hypothesized that, while water exited hot biomass in the form of water vapor instead of liquid water, as is typically the case in water-washing processes, a share of undesirable elements may still have been removed from biomass through vaporization, without necessitating any additional process for ash removal. Hence, the index values calculated according to the chemical analysis of biomass ash suggested that sunflower husk biochar (biocoal) resulting from the proposed two-stage torrefaction process may display fuel characteristics similar to biomasses whose combustion ash may form reduced levels of deposits on boiler surfaces. Therefore, the proposed technology holds the potential to improve solid fuel characteristics of biomass, targeting enhanced efficiency and sustainability of biomass-fired power plants.

Intercropping increases soil macroaggregate carbon through root traits induced microbial necromass accumulation

Microbial necromass, as part of persistent soil organic matter, plays a significant role in maintaining soil fertility and sustainability of agroecosystems. Intercropping, planting multiple crop species in the same field at approximately the same time, has been demonstrated to increase soil organic matter through enhanced biomass input. Nonetheless, little is known as to how intercropping affects microbial necromass accumulation in soils and the underlying microbiological mechanisms, particularly about microbial life strategies and network stability. Here, we investigated the carbon (C) accumulation mechanism of microbe-aggregate interactions using aggregate fractionation combined with microbial biomarkers as well as high-throughput sequencing in an 11-year maize/peanut intercropping field experiment. We found that intercropping increased soil organic carbon (SOC) and microbial necromass C in macroaggregates (>250 μm) compared with sole crops, and it was mostly accounted for by fungal necromass C. Within small macroaggregates (250–2000 μm), bacterial necromass C was positively correlated with r-strategy bacteria, and fungal necromass C was positively correlated with K-strategy fungi. Microbial inter-kingdom co-occurrence network analysis showed higher proportions of positive links in intercropping system than in sole crops, and the proportions of positive links positively correlated with fungal necromass C in macroaggregates (>250 μm). Path analysis revealed that intercropping increased SOC mainly through root traits induced microbial life strategies and microbial network stability, resulting in increased microbial necromass. In conclusion, crop diversity-driven changes in root traits induced microbial traits promote microbial necromass accumulation. A new mechanism elucidating the positive crop diversity effect on soil C sequestration is proposed.

Cover crops and soil health in rainfed and irrigated corn: What did we learn after 8 years?

AbstractDuration of cover crop (CC) management, CC biomass production, and other factors could impact how CC affects soil health. We studied the 8‐year cumulative impacts of winter rye (Secale cereale L.) CC on soil physical, chemical, and biological properties in rainfed and irrigated no‐till corn (Zea mays L.)‐based systems in the western US Corn Belt. Average annual CC biomass production was 0.56 ± 0.51 Mg ha−1 at the rainfed site and 0.98 ± 0.95 Mg ha−1 at the irrigated site. After 8 years, CC improved particulate organic matter (POM) and mean weight diameter of water‐stable aggregates (MWD) compared with no CC in the 0–5 cm soil depth at both sites. Cover crop increased total POM concentration by 2.8 mg g−1 at the rainfed site and by 13.4 mg g−1 at the irrigated site, while it increased MWD by 0.39 mm at the rainfed site and by 0.79 mm at the irrigated site. Also, CC increased soil C at a rate of 0.125 Mg ha−1 year−1 in the 0–5 cm depth but only at the rainfed site. Cover crop affected neither water infiltration nor available water but improved microbial biomass. Changes in other properties were site‐dependent. Cover crop improved many soil properties after 8 years even though measurement taken after 4 years showed no significant effect of CC, which indicates CC slowly impacts properties in this environment. Low CC biomass production and high biomass input from corn‐based systems may explain the slow soil response. In general, winter rye CC enhances near‐surface soil properties in the long term.

High starch duckweed biomass production and its highly-efficient conversion to bioethanol

This paper carried out a new attempt which combined nutrient starvation, uniconazole and elevated CO2 to increase duckweed biomass and starch content. At laboratory level, the highest growth rate and starch content reached up to 9.4 ± 0.2 g m−2 d−1 and 75.9 ± 3.3 %, leading to an estimated starch yield of 30.8 t ha−1 y−1. Furthermore, without any pretreatment, up to 88.4 ± 0.4 % of glucose from high starch duckweed biomass can be released. The enzymatic hydrolyzates can be efficiently converted to bioethanol by yeast and the ethanol yield based on duckweed biomass input (YE/B) reached up to 0.38 ± 0.01 g g−1 applying simultaneous saccharification and fermentation (SSF), which, to our knowledge, is the highest duckweed-to-ethanol yield thus far reported. Based on the data above-mentioned, an annual duckweed-based ethanol yield of 16.0 × 103 L ha−1 can be achieved, about 2.6 times higher than maize-based ethanol yield. This approach has achieved quick high starch accumulation in duckweed and demonstrated that duckweed can serve as a competitive starch feedstock for bioethanol production.

Afforestation triggers water mining and a single pulse of water for carbon trade-off in deep soil

Clarifying the water-root-carbon nexus in the entire root zone is crucial for unlocking the potential of afforestation in mitigating climate change. But the nexus in deep soil (depth > 1 m) remains poorly understood. Here we report contrasts in deep soil water and root distributions across 72 paired sites of adjacent farmlands, representing typical pre-afforestation conditions, and tree plantations, representing modern afforestation across the Loess Plateau of China. Ranging from 6 to 25 m of depth, these profiles included plantations of 13 tree species ranging from 1 to 25 years of age. The observations revealed sustained water mining in deep soil following afforestation with mean soil water decline of 75.2 ± 9.8 mm yr−1 that were accompanied by root deepening rates of 1.00 ± 0.06 m yr−1 with an associated biomass input of 0.18 ± 0.04 Mg C ha−1 yr−1. A water for carbon trade-off in deep soil become evident, likely involving a single pulse of C gains and water losses as no signs of soil rewetting under tree plantations where observed total soil water exhaustion that accumulated the equivalent of up to 2.8 years of mean annual precipitation inputs. The reported water-root-carbon nexus reveals overlooked hydrological costs and, more importantly, over-optimistic expectations of sustained C sequestration under afforestation that may rather represent a single-pulsed C gain supported by deep soil water exhaustion.

Estimation of syngas yield in hydrothermal gasification process by application of artificial intelligence models

Quality syngas production with higher moles of hydrogen and methane are the primary objective of gasification process which is dependent upon the process parameters and composition of biomass. However, it is always a costly and time-consuming task to get the optimum biomass composition and process parameters for quality syngas production. In this research, artificial intelligence (AI) algorithms have been applied for high quality syngas prediction with better moles fractions of hydrogen and methane using hydrothermal gasification (HTG). Comparative analysis of Convolutional Neural Network (CNN), Artificial Neural Network (ANN), Gradient Boost Regressor (GBR), Extreme Boost Regressor (XGB), and Random Forest Regressor (RFR) based algorithms have been done to select an optimal one. Ultimate analysis of biomass and process input parameters inlcuding temperature, pressure, percentage solid content of biomass, and resident time have been used as an input parameter for prediction models. Final comparative results of these AI models conclude that XGB has a better prediction result as compared to other with coefficient of determinant (R2) and mean square errors ranges from 0.85 to 0.95 and 0.008–0.01, respectively. Furthermore, process temperature and the resident time are the most contributing factors in mole fractions of hydrogen and methane. Higher hydrogen and oxygen contents in the biomass, significantly contributes to the production of quality syngas.

Synthesis and evaluation of metal-impregnated carbon cloth supplementation to improve anaerobic digestion performance from municipal sludge

This study investigated the effect of metal-impregnated carbon cloth (CC) supplementation on thermophilic anaerobic digestion (AD) improvement by utilizing municipal sludge as a biomass input. Four types of metal-impregnated CC nanocomposites (Fe/CC, Ni/CC, Ni/Fe/CC, NiPcS/Fe/CC) were synthesized from activated CC (A-CC) using hydrothermal synthesis and compared with untreated CC (U-CC) to evaluate their functional significance for enhanced AD. The main factors inspected were electrical conductivity (EC) and Brunauer–Emmett–Teller (BET) surface area. A-CC had the highest surface area of 386.15 m2/g, followed by Fe/CC, NiPcS/Fe/CC, Ni/CC and Ni/Fe/CC with 140.96, 52.27, 43.52 and 36.07 m2/g, respectively. The A-CC and Fe/CC reactors produced 3.45 and 2.70 times more methane than Control (without CC) in the first 9 days. In contrast, the methane production for U-CC, Ni/CC, Ni/Fe/CC and NiPcS/Fe/CC was only 0.87, 1.26, 1.01 and 1.29 times, respectively, compared to Control. At a higher BET surface (>350 m2/g), the surface area becomes a more dominant factor, and the increase of EC value (>2.9*104 1/Ω.m) does not have an impact on methane enhancement. Microbial community analysis revealed that A-CC had the highest abundances of Syntrophomonas, Coprothermobacter and methanogenic populations, including Methanothermobacter and Methanosarcina, within 3 days compared to Control and metal-impregnated CC. There were minimal changes in microbial community composition in metal-impregnated CC compared to the U-CC. The result implies that the efficacy of CC supplementation for AD upgrading largely depends on the higher surface area compared to metal impregnation or conductivity.

Is plant biomass input driving soil organic matter formation processes in grassland soil under contrasting management?

Grassland management practices vary in stocking rates and plant removal strategies (grazing versus mowing). They influence organic matter (OM) inputs, which were postulated as main controls of soil organic carbon (SOC) sequestration and might therefore control SOC stabilization. The aim of this study was to test this hypothesis by investigating the impacts of grassland harvesting regimes on parameters related to soil microbial functioning and soil organic matter (SOM) formation processes. We used a thirteen-year experiment in Central France under contrasting management (unmanaged, grazing with two intensities, mowing, bare fallow) to establish a carbon input gradient based on biomass leftovers after harvest. We investigated microbial biomass, basal respiration and enzyme activities as indicators of microbial functioning, and amino sugar content and composition as indicator of persistent SOM formation and origin through necromass accumulation. Responses of these parameters to carbon input along the gradient were contrasting and in most cases unrelated. Only the microbial C/N ratio and amino sugar contents showed a linear response indicating that they are influenced by plant-derived OM input. Other parameters were most probably more influenced by root activity, presence of herbivores, and/or physicochemical changes following management activities impacting soil microbial functioning. Grassland harvesting strategies influence SOC sequestration not only by changing carbon input quantity, but also through their effects on belowground processes possibly related to changing carbon input types and physiochemical soil properties.

Factors affecting Cladophora growth in the eastern basin of Lake Erie: Analysis of a monitoring dataset (2012–2019)

Cladophora is a naturally occurring benthic alga in the Great Lakes which can reach nuisance levels in the nearshore, leading to beach closures and other impacts. A monitoring program was initiated in 2012 in the eastern basin of Lake Erie to identify ecological factors driving its growth. Inflows from the Grand River, the largest river to the north shore, were generally positively associated with phosphorus concentrations in the nearshore and negatively associated with light reaching the lakebed. At the depths sampled (3 m–18 m), Cladophora was strongly influenced by light availability, and due to shading by the Grand River plume, an overall negative association was found between Cladophora biomass and phosphorus inputs. Phosphorus limitation was only observed at shallow sites farthest from the Grand River. Positive associations between dreissenid mussel coverage and both Cladophora biomass and tissue phosphorus suggest that nutrient cycling by dreissenids supports Cladophora growth. Our results indicate that i.) the Grand River has a strong influence on nearshore nutrient levels and water clarity; and ii.) Cladophora is limited by both phosphorus and light to varying degrees within the study area, although light appears to be the dominant factor, at least at these depths, years, and locations. The implication that phosphorus reductions could lead to increased Cladophora biomass by improving light conditions will need to be considered carefully against the known historical success of controlling nuisance algae through nutrient management.

A resource-based and institutional theory-driven model of large-scale biomass-based bioethanol supply chains: An emerging economy policy perspective

The wide-spread dependence of transportation sector on the ever-depleting and greenhouse gas emitting fossil fuels when burnt has raised considerable energy security and environmental concerns. Consequently, countries around the world have positioned biofuels as a center stage alternative to fossil fuels in their national policies to provide energy security and carbon emission control. In this regard, the paper conducts a feasibility assessment of setting-up large-scale supply chain of bioethanol (i.e., a biofuel variant) based on the regional availability of agricultural residues. Critical resources and capabilities requirements and governance attributes for bioethanol supply chains are explored using the resource-based view and institutional theory lenses. An agricultural residues (as biomass inputs) based bioethanol supply chain (BESC) model is proposed to incorporate the economic and environmental optimality considerations for an agro-climatic region. A case study of the Punjab State in India is used as an application of the proposed BESC model. Findings suggest that sustainable BESC configurations can be achieved differently for different agricultural residues. Comparative analyses, trade-off scenarios, and sustainability assessments of various agricultural residues-based BESC configurations are conducted. The policy implications of the priority areas are discussed within the bounds of India's biofuel policy.

Active plant biomass inputs influence pore system functioning in no-till soils

Available knowledge about the exact impact of plant growth on the properties and functioning of no-till soils is somewhat limited, especially in tropical and subtropical regions. The starting hypothesis for this work was that long-term active plant biomass Input-APBI (aboveground plant shoot biomass) would improve pore system functioning in surface and subsurface soil layers by playing different, complementary roles in a previously degraded subtropical Acrisol. The hypothesis was checked by examining the results of a 34-yr field experiment involving five different cropping systems, namely: bare soil (BS), perennial pasture (PAST), oat/maize (O/M), oat + vetch/maize (O + V/M) and oat + vetch/ maize + cowpea (O + V/M + C). The soil was supplied with APBIs varying from 0.13 to 1.48 kg dry matter ha−1 yr−1. The APBIs for each cropping system were very low (BS), low (O/M), medium (O + V/M), high (O + V/M + C), and very high (PAST). The surface (0–5 cm) and subsurface (5–15 cm) soil layer were analyzed for static and dynamic properties of the pore system including bulk density; total, macro, and microporosity; the ability of the system to conduct air and water; continuity in soil pores; and plant-available water capacity. Micromorphological images of the soil revealed a complex pore network whose structure and functioning were both improved by the action of plants. In the surface soil layer, very high APBIs from pasture and high inputs from O + V/M + C increased total porosity by 11 and 14 %, respectively; pore continuity (Ncont) by 11 and 40 %, respectively; and microporosity by 31 and 23 %, respectively —all relative to bare soil. In the subsurface soil layer, pasture, and O + V/M + C decreased Ncont by 44 and 40 %, respectively, but increased water permeability (kw) by a factor of 6.5 and 7, respectively. In addition, very high APBIs increased continuity and permeability to air in macropores relative to BS. Organized large macropores in the subsurface soil layer efficiently conducted water and air from the soil surface and acted as bridges between the surface and subsurface soil layer. Overall, our findings suggest that APBIs helped develop a pore system with differential properties and complementary functions that influenced water infiltration and air fluxes in the surface soil layer, and water availability to crops in the subsurface soil layer, through long-term self-organization in the system. Future research with a view to understanding the influence of species richness and roots on physical quality in no-till soils is recommended.

Assessment of electrified ethylene production via biomass gasification and electrochemical CO reduction

The chemical industry needs new methods for sourcing carbon-containing feedstocks from renewable sources to decrease CO2 emissions and reduce reliance on fossil fuels. Ethylene, a crucial base chemical used for making polymers and ethylene oxide, is primarily produced through steam cracking of fossil feedstocks. However, an evolving technology is the electrochemical reduction of CO2 or CO to produce ethylene. The study assesses the environmental, economic and energetic performance of a new biomass-based process that produces ethylene based on the electrochemical reduction of CO. The results are based on mass and energy balances from process simulation. The CO is produced by either gasification of biomass or combustion of biomass with CO2 capture and CO2 electrolysis. Besides ethylene, the process produces acetic acid, ethanol, oxygen and hydrogen as by-products which are purified and sold. The annual output varies between 36 and 68 kt ethylene with a biomass input of 157 kt. The levelized cost of ethylene ranges from 3,920 to 7,163 €/t with the gasification routes being the most cost-effective. The ethylene price is heavily dependent on electricity price, current density, operating voltage, and by-product prices. The carbon efficiency of the gasification-based routes is lower (64%) than the combustion-based routes (85%–86%). However, the energy efficiency is higher for the gasification-based routes (42%) compared to the combustion-based routes (28%). Conversion of ethanol to ethylene increases the ethylene yield with minimal impacts on the ethylene price. In terms of CO2 emissions, the gasification-based routes show lower emissions. Scenarios using wind power show a significant emission reduction potential compared to fossil products.

Invasive herbivores shape food web structure: European rabbit and hare acting as primary prey are conservation challenges

As part of the current global change scenario, invasive species have caused many direct impacts on native biodiversity and the interactions among species. European rabbits and hares are two herbivore species that have been introduced worldwide, displacing native species within their trophic level, but also affecting native predators. Both species have become extremely abundant in their exotic distributions, becoming primary prey for many predators, a function that they also play in their native ranges. These relatively new and strong interaction links created with their consumers have the potential to destabilize food webs by precluding the occurrence of weaker links. Here, we have compiled the diet of 32 predator species from three food webs and compared them: one in Europe, where these species are native, and two where they are introduced, in South America and Oceania. We found that these lagomorphs are the primary prey in all study sites, generating a dietary shift of predators in the invaded regions. In all food webs studied, these two preys channeled most of the biomass input towards the higher trophic level, generating the strongest interaction links, affecting the food web configuration and stability. They destabilize food web structure by homogenizing predators' diets, augmenting their niche overlap and web vulnerability. Moreover, rapid population changes of these prey, either natural (e.g., diseases) or anthropic (e.g., control measures), create new conservation challenges for predators and scavengers. This highlights that invasive species can strongly affect interactions among species and it should be considered in management and conservation actions.

Biochar production from late-harvest grass – Challenges and potential for farm-scale implementation

Grasslands play a crucial role in European agriculture and ecology, but are often underutilized due to low-value end-products. The utilisation of late-harvest grass for biochar and heat generation on farm-level is being studied as a potential negative emissions technology. Technical (energy provision and carbon sink), economic (cost vs. benefit), political (regulatory framework) and social (SWOT) perspectives are being evaluated. Technical feasibility has been demonstrated with three different farm-scale technologies and the energetic and carbon-sink potential evaluated. When a continuously operating allothermal unit is evaluated, 35 % of the input biomass energy content can be utilized for heating a farm, in combination with the potential to provide a carbon sink. The cost-benefit analysis shows important monetary savings when including the agronomic value (based on the market price) of the produced biochar. An assessment of the regulatory framework of biochar production in Germany presents a multitude of regulations applying to such technologies some of which provide a hurdle to navigate and may incur excessive costs for farmers as small-scale biochar producers. A SWOT analysis of a case in Brandenburg, Germany highlights strengths and opportunities, but also obstacles such as lack of infrastructure and regulatory support. This study highlights the need for further development of suitable technology and research on the long-term economic and carbon sink potential of biochar.

Increasing carbon efficiency for DME production from wheat straw and renewable electricity – Analysis of 14 system layouts

Liquid fuels like dimethyl-ether (DME), produced from biomass and electricity are crucial for decarbonizing the shipping industry. In this work, the production of DME from wheat straw through gasification is presented. It was shown how the process can be optimized by using 1) two-stage instead of one-stage DME synthesis, 2) partial oxidation of the produced gas and 3) a hydrogen quench for high-temperature reverse water gas shift reactions. The investigation was conducted by stepwise introducing the different process steps, leading to investigating 14 different plant layouts. This enabled a systematic analysis of the influence of different process steps by looking at the changes in carbon efficiency and energy efficiency. In all plants, DME and bio-ash, which acts as a soil amendment and carbon sink, were produced. 10 of the 14 plants additionally produced high-quality bio-oil. The analysis showed that all the introduced measures increased the carbon efficiency of the plants. At the same time, they increased the net electricity consumption. The highest energy efficiency reached was 57.5 %. A different plant reached the highest carbon efficiency with 84.0 %.,while having the highest net electricity consumption (45.2 MW at a biomass input of 50 MW (LHV)).

Sanitization of Biomass in Agricultural Biogas Plants Depends on the Type of Substrates.

Large-scale pig farming is associated with the production of large amounts of animal excrement, which, after processing into the form of, e.g., slurry, are managed on agricultural land as natural fertilizers. The utilization of pig manure on agricultural land in an excessive and uncontrolled manner may pose a threat to zoonoses due to the significant amounts of potentially pathogenic microorganisms within its content. This study aims to determine the impact of the methane fermentation process carried out in two agricultural biogas plants on the efficiency of sanitization of pig slurry, input biomass, and digestate. The biogas plants differed in terms of the substrate used; one used pig slurry from a maternal (breeding) farm (BP-M), and the other utilized pig slurry from a fattening farm (BP-F). The physicochemical analyses showed that the slurry, input biomass, and digestate from the BP-F were characterized by a significantly higher contents of organic dry matter, ash, and ammonium nitrogen than the slurry, input biomass, and digestate from the BP-M. The parameters of the methane fermentation process, including temperature and pH, reached higher values in the BP-F compared to the BP-M. The microbiological analyses led to the conclusion that the efficiency of sanitization of input biomass, including pig slurry, was significantly higher in the BP-F compared to the BP-M. Due to the above findings, locating biogas plants near pig fattening farms should be recommended.