Reduce Methane Emissions Research Articles

The Path to Net-Zero in Dairy Production: Are Pronounced Decreases in Enteric Methane Achievable?

Achieving net-zero greenhouse gas (GHG) emissions in dairy production will require >50% reduction in enteric methane (CH4) emissions together with elimination of emissions from feed production, additional carbon sequestration, reduction in manure emissions, anaerobic digestion of manure, and decreased reliance on fossil fuel energy. Over past decades, improved production efficiency has reduced GHG intensity of milk production (i.e., emissions per unit of milk) in the United States, but this trend will continue only if cows are bred for increased efficiency. Genetic selection of low-CH4-producing animals, diet reformulation, use of feed additives, and vaccination show tremendous potential for enteric CH4 mitigation; however, few mitigation strategies are currently available, and added cost without increased revenue is a major barrier to implementation. Complete elimination of CH4 emissions from dairying is likely not possible without negatively affecting milk production; thus, offsets and removals of other GHGs will be needed to achieve net-zero milk production.

Climate change mitigation and adaptation for rice-based farming systems in the Red River Delta, Vietnam

Abstract Background Rice is a major contributor to anthropogenic greenhouse gas (GHG) emissions, primarily methane, and at the same time will be negatively impacted by regional climate changes. Identifying rice management interventions to reduce methane emissions while improving productivity is, therefore, critical for climate change mitigation, adaptation, and food security. However, it can be challenging to conduct multivariate assessments of rice interventions in the field owing to the intensiveness of data collection and/or the challenges in testing long-term changes in meteorological and climate conditions. Process-based modeling, evaluated against site-based data, provides an entry point for evaluating the impacts of climate change on rice systems and assessing the impacts, co-benefits, and trade-offs of interventions under historical and future climate conditions. Methods We leverage existing site-based management data to model combined rice yields, methane emissions, and water productivity using a suite of process-based coupled crop-soil model experiments for 83 growing sites across the Red River Delta, Vietnam. We test three rice management interventions with our coupled crop-soil model, characterized by Alternate Wetting and Drying (AWD) water management and other principles representing the System of Rice Intensification (SRI). Our simulations are forced with historical as well as future climate conditions, represented by five Earth System Models for a high-emission climate scenario centered on the year 2050. We evaluate the efficacy of these interventions for combined climate change mitigation and adaptation under historical and future climate change. Results Two SRI interventions significantly increased yields (one by over 50%) under historical climate conditions while also reducing (or not increasing) methane emissions. These interventions also increase yields under future climate conditions relative to baseline management practices, although climate change decreases absolute yields across all management practices. Generally, where yield improved, so did crop water-use efficiency. However, impacts on methane emissions were mixed across the sites under future climate conditions. Two of the interventions resulted in increased methane emissions, depending on the baseline management point of comparison. Nevertheless, one intervention reduced (or did not significantly increase) methane under both historical and future climate conditions and relative to all baseline management systems, although there was considerable variation across five selected climate models. Conclusions SRI management principles combined with high-yielding varieties, implemented for site-specific conditions, can serve climate change adaptation and mitigation goals, although the magnitude of future climate changes, particularly warming, may reduce the efficacy of these interventions with respect to methane reductions. Future work should better bracket important sensitivities of coupled crop-soil models and disentangle which management and climate factors drive the responses shown. Furthermore, future analyses that integrate these findings into socio-economic assessment can better inform if and how SRI/AWD can potentially benefit farmer livelihoods now and in the future, which will be critical to the adoption and scaling of these management principles.

In Vitro Plant Regeneration of Sulla coronaria from Floral Explants as a Biotechnological Tool for Plant Breeding

Sulla coronaria L. Medik., a biennial forage legume typical of the Mediterranean basin, plays a significant role in foraging systems due to its high nutritional value, ability to increase ruminant live weight, and potential to reduce methane emissions. However, its allogamous nature complicates genetic improvement and the development of new varieties with desired traits. Given these challenges, this study aims to develop, for the first time, a successful protocol for the in vitro meristematic shoot regeneration of S. coronaria. The experiment utilizes four different flower explants (anther with filament, ovary, petals, and whole immature flower) collected from twenty distinct S. coronaria biotypes with three plant growth regulator (PGR) combinations and under both light and dark conditions. In terms of the regeneration response, the key factors appear to be the combinations of PGRs and the type of explant used. The interactions between all the factors do not seem to be significant.

Hydrogen-rich water 400ppb as a potential strategy for improving ruminant nutrition and mitigating methane emissions.

The objective of this study was to evaluate the effects of different concentrations of hydrogen-rich water (HRW) on in vitro rumen fermentation characteristics and the dynamics of bacterial communities. The experiment included four treatment groups: a control (CON) and hydrogen-rich water (HRW) at 200, 400, and 800 ppb. Each group was analyzed at 12-hour (h) and 48-hour (h) time points with five replicates, totaling 40 samples. The experimental results highlighted the HRW800ppb group as the top production in terms of gas production and CH4 content. In contrast, the HRW200ppb group exhibited significantly lower methane levels at both 12h and 48h (P < 0.05). Regarding rumen fermentation, the HRW400ppb group significantly increased the levels of ammonia nitrogen (NH3-N) and microbial crude protein (MCP) at 12h fermentation, but reduced the dry matter degradation rate (P < 0.05). After 48h, the HRW400ppb group had highest MCP content (P < 0.05), but no significant differences in NH3-N and dry matter degradation rate compared with the CON group (P > 0.05). Although HRW did not significantly benefit the synthesis of total volatile fatty acids (TVFA) and individual VFA, the HRW800ppb group significantly increased the ratio of acetate to propionate (P < 0.05). Based on CH4 emissions and MCP synthesis, we selected the HRW400ppb group for subsequent bacterial community analysis. Bacterial community analysis showed that at 12h, compared with the CON group, the Bacterial community analysis revealed that the HRW400ppb group had significant increases in the Simpson index, Firmicutes, Streptococcus, Schwartzia, Prevotellaceae_YAB2003_group, and Oribacterium, and decreases in Prevotella, Ruminobacter, Succinivibrio, unclassified_Succinivibrionaceae, and Prevotellaceae_UCG-003 (P < 0.05). At 48h, the Prevotellaceae_YAB2003_group and Oribacterium abundances continued to rise significantly, while Rikenellaceae_RC9_gut_group and Succiniclasticum abundances fell in the HRW400ppb group (P < 0.05). Correlation analysis indicated a negative link between CH4 and Streptococcus, and a positive correlation between the abundance of Rikenellaceae_RC9_gut_group and CH4. Collectively, these results indicate that HRW can modulate rumen fermentation and microbial community structure to reduce methane emissions without significantly affecting VFA synthesis, highlighting its potential as drinking water for enhancing ruminant nutrition and mitigating the environmental impact of livestock farming.

A new strategy for greenhouse gas emission reduction in the anaerobic/anoxic/oxic biological treatment process using exogenous N-acyl-homoserine lactones, a quorum-sensing signaling molecules

ABSTRACT In this study, the impact of exogenous N-acyl-homoserine lactones (AHLs) on greenhouse gas (GHG) emissions in anaerobic/anoxic/oxic (A/A/O) systems was analyzed by manipulating the type and dosage of AHLs. The mechanism behind AHLs’ effects on GHG emissions was explored through changes in microbial community structure. Findings revealed that N-octanoyl-homoserine lactone (C8-HSL) and high-dose N-dodecanoyl-homoserine lactone (C12-HSL) increased GHG emissions, while low-dose C12-HSL decreased them. Moreover, C8-HSL and high-dose C12-HSL promoted methane (CH4) and nitrous oxide (N2O) production by affecting sludge particle size. Bacterial community analysis highlighted Acinetobacter and Flavobacterium's roles in N2O emissions and acetate methanogens in methane synthesis. Metabolic pathway analysis showed that the acetic acid (CH3COOH) methanogenic pathway was the main methanogenic pathway; C8-HSL and C12-HSL influenced methane emission by affecting the methanogenic pathway and N2O emission by changing nitrous oxide reductase (Nos) abundance. This research underscores AHL-based quorum sensing's potential in mitigating GHG emissions during activated sludge wastewater treatment, offering insights into their application and impact on key microbial activities. Limitations include the absence of methane emission reduction by signaling molecules and the need for further investigation into their effects on sludge accumulation.

An assessment of China’s methane mitigation potential and costs and uncertainties through 2060

China, the world’s largest methane emitter, is increasingly focused on methane mitigation in support of its climate goals, but gaps exist in the understanding of key methane sources, as well as mitigation opportunities and their associated uncertainties. We use a bottom-up modeling approach with updated methane emission projections and abatement cost analysis to account for additional sources, uncertainties, and mitigation measures in China’s energy and agricultural sectors. Here we show the significant cost-effective potential for reducing methane emissions in China by 2030, with 660 million tonnes of carbon dioxide equivalent possible with average negative abatement costs of US$6.40 per tonne CO2e. Most of this potential exists in the energy sector, particularly coal mining, but the greater potential will shift towards agriculture by 2060. Aquaculture and biochar applications in rice cultivation have net economic benefits but need greater support for deployment, while new mitigation measures will be needed for remaining emissions from enteric fermentation, rice cultivation, and wastewater.

Methane Emissions from Oil and Natural Gas Operations—30 Percent Reduction by 2030 Possible if Domestic and International Actions “Stay the Course”

When sworn into office in January 2021, the Biden–Harris Administration—through the National Climate Task Force—launched an ambitious, whole‐of‐government initiative to significantly double efforts and reduce methane emissions from the oil and natural gas sector, landfills, agriculture, and other lesser sources. These initiatives were documented in the U.S. Methane Emissions Reduction Action Plan, which proposed to use regulations, catalytic financial incentives, transparency and disclosure of actionable data, together with public and private partnerships, to identify and reduce methane emissions. President Biden's Build Back Better agenda was designed to accelerate, through investments, many of these domestic methane emissions reduction efforts.

Selection indexes in terms of functional features in modern dairy cattle breeding in Europe

Abstract The increase in demand for dairy products requires continued progress in dairy farming for a sustainable supply. Europe, known as the world's leading milk producer, plays a key role in meeting this growing demand. Modern dairy farming has moved beyond its historical focus on milk yield and now focuses on functional traits such as udder health, fertility and calf survival. As a result, selection indicators have become essential tools, combining multiple attributes to support selective decisions. However, these rates show considerable variability across countries, reflecting their distinct breeding goals. Poland's production and functionality (PF) Index emphasizes production and functional traits to enhance dairy cattle. Portugal uses the total economic merit (M€T) and total performance index (IPT) for a broader assessment covering a wider range of traits. Ukraine is transitioning towards a more comprehensive breeding system incorporating stress tolerance and longevity. Factors such as climate change and the need for sustainable practices drive this evolution, underscoring the economic importance of traits beyond mere production. Future trends may include features such as feed efficiency, methane emissions reduction and stress resistance. Diverse breeding objectives across countries lead to different selection index constructions, essential for effective selection, ranking and breeding of superior individuals. This comprehensive review offers insight into constantly evolving dairy farming strategies in Europe, with a focus on Poland, Portugal and Ukraine, while highlighting the key role of functional traits in shaping the future of dairy farming.

Investigation on the methane emissions from permeation of urban gas polyethylene pipes under the background of hydrogen-mixed natural gas transportation

Methane, a more potent greenhouse gas than carbon dioxide, aggravates the greenhouse effect of ecological environment through its emissions. When transporting hydrogen-mixed natural gas through urban polyethylene pipes, methane will be emitted due to the permeation characteristic of polyethylene pipe material. Therefore, it is crucial to pay attention to the methane emissions from permeation of polyethylene pipes for protecting the environment and climate. In this paper, the solubility and diffusion coefficients of methane within hydrogen-mixed natural gas in polyethylene pipe materials are calculated through the Monte Carlo method and molecular dynamics simulation to determine the permeation coefficient of methane. Simultaneously, the methane emissions and equivalent carbon dioxide emissions of the hydrogen-mixed natural gas in polyethylene pipes are investigated. Results indicate the methane solubility coefficient decreases with increasing temperature and hydrogen mixing ratio. The methane diffusion and permeation coefficients increase with the rising temperature and pressure, and decreasing hydrogen mixing ratio. The pressure exerts minor influence while the temperature and hydrogen mixing ratio have more significant impact. That is, the lower the temperature and the higher the hydrogen mixing ratio, the less methane emissions caused by permeation. Therefore, the effective reduction of methane emissions can be achieved by adding the insulation layer to mitigate the impact of high temperature and increasing the hydrogen mixing ratio. For example, for the polyethylene pipe with the operating pressure of 4 bar and the size specification of SDR11, when the temperature drops from 300 K to 260 K, the methane emissions of hydrogen-mixed natural gas with hydrogen mixing ratios of 0 vol%, 20 vol%, 50 vol% and 80 vol% will be drastically reduced by 73.3%, 74.4%, 77.2% and 78.5% respectively, and when 20 vol%∼80 vol% hydrogen are mixed in the natural gas at 260 K, 300 K and 310 K, the methane emissions will be effectively reduced by 26.7%∼85.6%, 23.3%∼82.1% and 23.9%∼82.4% respectively. The findings of this study can serve as guidance for reducing the methane emissions from permeation of polyethylene pipes transporting hydrogen-mixed natural gas.

Ditch emissions partially offset global reductions in methane emissions from peatland drainage

Peatlands are globally important carbon sinks but are frequently drained. Drainage activities reduce overall methane emissions; however they are often accompanied by the construction of ditches, which are potential methane emission hotspots. Yet, the offsets of methane emissions from creating ditches in peatlands under different climate zones and land-use types remain unclear. Here we conducted a global meta-analysis by compiling annual methane emissions from paired near-pristine peatlands and terrestrial portion of drained peatlands and ditches to address this issue. Results showed that ditches occupy approximately 3.8 (95% confidence interval: 3.1~4.4)% of all drained peatlands. Ditches emit 695 (511~898) kg ha−1 yr−1 methane overall, with the highest emissions observed in (sub)tropics. Globally, ditch emissions offset approximately 12 (10~14)% for reductions in methane emissions from peatland drainage. Our findings demonstrate the importance of including ditch methane emissions to quantify emission factors for regional to global peatlands affected by drainage.

Programming rumen microbiome development in calves with the anti-methanogenic compound 3-NOP

The aim of this study was to establish a distinctive rumen microbial and fermentation profile using the anti-methanogenic compound 3-NOP to assess dam effect, and nutritional intervention of the juvenile offspring on microbial structure and function of rumen up to 12 months of age, once the treatment was withdrawn. Forty-eight pregnant heifers (H) and their future offspring (C) were allocated to either Control (-) or 3-NOP (+) treatment resulting in four experimental groups: H+/C+, H+/C-, H-/C + and H-/C-. Animals were treated from 6 weeks prior to calving until weaning, with the offspring monitored until 12 months of age. Rumen fluid samples and methane measurements using the Greenfeed system were collected during the trial. Results supported the mode of action of the compound, with a shift in fermentation from acetate to propionate, increases in branched chain fatty acids and formic acid in the 3-NOP treated animals. Similar shifts in microbial populations occurred in 3-NOP treated animals with lower abundances of rumen methanogen populations, increases of bacterial groups Succiniclasticum spp, Candidatus Saccharimonas. Fibrobacter and the families Prevotellaceae and Succinivibrioacea. and the protozoa Entodinium. Early life intervention had an enduring impact on the rumen microbial structure of young animals up to 28 weeks post weaning, however the effect was diminished once 3-NOP was withdrawn. Interestingly, a group of young animals emitted significantly less methane (15%) than the animals that did not receive the treatment during their juvenile stage. Our results suggest a higher resemblance of the young calf microbiome to a low methane adult and that early life colonisation of the rumen persists through to later life with the pre-weaning microbiome comprising ~ 65% of the yearling animal. Further research needs to be performed to determine the timing and dose of 3-NOP for new-born calves that can sustain a reduction in methane emissions after the treatment is withdrawn, under extensive grazing or controlled conditions.

Burp tax: Regulation and revenue potential in Indonesia

The increasingly urgent phenomenon of climate change requires concrete actions from various sectors, including the livestock sector which is a significant contributor to greenhouse gas emissions, particularly methane. This study explores the potential of implementing Burp Tax in Indonesia as a regulatory mechanism to reduce methane emissions from beef and dairy cattle farms. By referring to New Zealand's experience as a Burp Tax pioneer, this study analyzes the policy scheme that includes tax subjects, tax objects, tariffs, and fair and efficient collection mechanisms. In addition, this study identifies various obstacles that may be faced in the implementation of Burp Tax in Indonesia and provides recommendations to support the national commitment in achieving the Zero Emission target in 2045/2060. The research used qualitative methods with literature study data collection techniques. The research concludes that there is great potential for the imposition of Burp Tax, so that in addition to being a form of effort to reduce methane emissions from beef and dairy cattle farms, Burp Tax can also increase the portion of state revenue from the taxation sector. The specific tariff scheme is IDR30/KgCH4 with tax subjects in the beef and dairy cattle farming sector, including individuals with 30 cows and business entities. However, it is important to note that the imposition of Burp Tax may have an economic impact on livestock business actors and affect the price of meat and milk commodities. Therefore, further studies are needed regarding the potential and impact of Burp Tax implications in Indonesia. The results of this study are expected to make a significant contribution to the development of sustainable taxation policies that are responsive to the challenges of climate change.

Polyphenol rewiring of the microbiome reduces methane emissions.

Methane mitigation is regarded as a critical strategy to combat the scale of global warming. Currently, about 40% of methane emissions originate from microbial sources, which is causing strategies to suppress methanogens, either through direct toxic effects or by diverting their substrates and energy, to gain traction. Problematically, current microbial methane mitigation knowledge derives from rumen studies and lacks detailed microbiome-centered insights, limiting translation across ecosystems. Here we utilize genome-resolved metatranscriptomes and metabolomes to assess the impact of a proposed methane inhibitor, catechin, on greenhouse gas emissions for high-methane-emitting peatlands. In microcosms, catechin drastically reduced methane emissions by 72-84% compared to controls. Longitudinal sampling allowed for reconstruction of a novel catechin degradation pathway involving Actinomycetota and Clostridium, which break down catechin into smaller phenolic compounds within the first 21 days, followed by degradation of phenolic compounds by Pseudomonas_E from days 21 to 35. These genomes also co-expressed hydrogen-uptake genes, suggesting that hydrogenases may act as a hydrogen sink during catechin degradation, depriving methanogens of substrates. This was supported by decreased gene expression in hydrogenotrophic and hydrogen-dependent methylotrophic methanogens under catechin treatment. We also saw reduced gene expression from genomes inferred to be functioning syntrophically with hydrogen-utilizing methanogens. We propose that catechin metabolic redirection effectively starves hydrogen-utilizing methanogens, offering a potent avenue for curbing methane emissions across diverse environments including ruminants, landfills, and constructed or managed wetlands.

Assessing the design of integrated methane sensing networks

Abstract While methane is the second largest contributor to global warming after carbon dioxide, it has a larger warming effect over a much shorter lifetime. Despite accelerated technological efforts to radically reduce global carbon dioxide emissions, rapid reductions in methane emissions are needed to limit near-term warming. Being primarily emitted as a byproduct from agricultural activities and energy extraction, methane is currently monitored via bottom-up (i.e., activity level) or top-down (via airborne or satellite retrievals) approaches. However, significant methane leaks remain undetected and emission rates are challenging to characterize with current monitoring frameworks. In this paper, we study the design of a layered monitoring approach that combines bottom-up and top-down approaches as an integrated sensing network. By recognizing that varying meteorological conditions and emission rates impact the efficacy of bottom-up monitoring, we develop a probabilistic approach to optimal sensor placement in its bottom-up network. Subsequently, we derive an inverse Bayesian framework to quantify the improvement that a design-optimized integrated framework has on emission-rate quantifications and their uncertainties. We find that under realistic meteorological conditions, the overall error in estimating the true emission rates is approximately 1.3 times higher, with their uncertainties being approximately 2.4 times higher, when using a randomized network over an optimized network, highlighting the importance of optimizing the design of integrated methane sensing networks. Further, we find that optimized networks can improve scenario coverage fractions by more than a factor of 2 over experimentally-studied networks, and identify a budget threshold beyond which the rate of optimized-network coverage improvement exhibits diminishing returns, suggesting that strategic sensor placement is also crucial for maximizing network efficiency.

Impact of methane and other precursor emission reductions on surface ozone in Europe: scenario analysis using the European Monitoring and Evaluation Programme (EMEP) Meteorological Synthesizing Centre – West (MSC-W) model

Abstract. The impacts of future methane (CH4) and other precursor emission changes are investigated for surface ozone (O3) in the United Nations Economic Commission for Europe (UNECE) region excluding North America and Israel (the EMEP region, for European Monitoring and Evaluation Programme) for the year 2050. The analysis includes a current legislation (CLE) and maximum feasible technical reduction (MFR) scenario, as well as a scenario that combines MFRs with an additional dietary shift that also meets the Paris Agreement objectives with respect to greenhouse gas emissions (LOW). For each scenario, background CH4 concentrations are calculated using a probabilistic Earth system model emulator and combined with other precursor emissions in a three-dimensional Eulerian chemistry-transport model. While focus is placed on peak season maximum daily 8 h average (MDA8) O3 concentrations, a range of other indicators for health and vegetation impacts are also discussed. Our analysis shows that roughly one-third of the total peak season MDA8 reduction achieved between the 2050 CLE and MFR scenarios is attributable to CH4 reductions, resulting predominantly from CH4 emission reductions outside of the EMEP region. The impact of other precursor emission reductions is split nearly evenly between the reductions inside and outside of the EMEP region. However, the relative importance of CH4 and other precursor emission reductions is shown to depend on the choice of O3 indicator, though indicators sensitive to peak O3 show generally consistent results. The analysis also highlights the synergistic impacts of CH4 mitigation as reducing solely CH4 achieves, beyond air quality improvement, nearly two-thirds of the total global warming reduction calculated for the LOW scenario compared to the CLE case.

Dietary Conversion from All-Concentrate to All-Roughage Alters Rumen Bacterial Community Composition and Function in Yak, Cattle-Yak, Tibetan Yellow Cattle and Yellow Cattle.

The experiment was to compare the effects of switching all-concentrate to all-roughage diets on rumen microflora and functional metabolism of yak, cattle-yak, Tibetan yellow cattle and yellow cattle living in different altitudes. A total of 24 yaks, cattle-yaks, Tibetan yellow cattle and yellow cattle with a similar weight and good body condition aged 3.5 years were selected and divided into four groups according to species. They were fed a concentrate diet with 40% soybean meal and 60% corn meal for the first month (C group) and a roughage diet with dry corn stalks (100%) for the second month (R group); the formal experimental period was 60 d. These results showed that the conversion had a significant effect on the rumen microflora structure of the four herds, and the biggest difference between concentrate and roughage diets was yak and cattle-yak, followed by Tibetan yellow cattle and yellow cattle. At the phylum level, Bacteroidetes and Firmicutes still predominate in all groups. Compared with the C groups, the relative abundance of Lentisphaerae and Kiritimatiellaeota increased in all R groups, and Lentisphaerae was significantly increased in yak and cattle-yak (p < 0.05). At the genus and species levels, Prevotella had the highest abundance, and the relative abundances of Prevotella, Ruminococcus, Sarcina and Ruminobacter in R groups were lower, while the abundances of other differential genera, including Methanobrevibacter, Fibrobacter, Treponema, Eubacterium, Butyrivibrio, Succinivibrio and Succinimonas, were all higher. Roughage diets increased the number of unique genes and functional genes encoding different CAZymes in rumen microorganisms in all four herds. In the functional contribution analysis, with the exception of ABC transporters and methane metabolism, Prevotella was the main contributor to almost all of these functions. In methane metabolism, Methanobrevibacter had the highest relative abundance, followed by Prevotella, Clostridia and Bacteroidales in all groups. Compared with Tibetan yellow cattle and yellow cattle, yaks and cattle-yaks have better adaptability to roughage, and its utilization rate can be fully improved to reduce methane emission. The study indicates that when four herds are converted to high roughage at the later stage of feeding, the growth and reproduction of rumen microorganisms are affected, and the abundance and diversity of rumen microorganisms are increased to varying degrees. The transformation of concentrate to roughage diet can change the metabolic pathways of rumen microorganisms in yaks and finally affect the fermentation mode of rumen. The above results provide a theoretical basis for the research and development of fattening feeds for yaks, cattle-yaks, Tibetan yellow cattle and yellow cattle and the intensive feeding of livestock on the plateau.

Game changer for anaerobic fermentation of paper mulberry: Sucrose-loaded biochar enhancing microbial communities and lactic acid fermentation

This study investigated biochar effects, either alone or combined with sucrose, on fermentation quality, microbial communities, and in vitro rumen digestion of anaerobic fermented paper mulberry. The biochar alkaline functional groups bind to lactic acid, reducing acid inhibition and promoting Lactiplantibacillus proliferation. Owing to the low sugar content of paper mulberry, lactic acid bacteria in the biochar group primarily underwent heterofermentation, resulting in the lowest lactic and highest acetic acid contents. Treated with sucrose-loaded biochar, the increased substrate supported homofermentation, leading to the highest lactic and lowest acetic acid contents, with a 15.0 % increase in lactic acid and a 22.2 % decrease in ammoniacal nitrogen compared with the control after 75 days. In vitro rumen tests showed that the biochar-sucrose group had the highest dry matter degradation rate (45.9 %) and a 24.2 % reduction in methane emissions. Concludingly, sucrose-loaded biochar is recommended as effective for lactic acid production under anaerobic conditions.

The effect of biochar supplementation on feed utilization, milk production and methane emission in lactating dairy cows

There is an increasing trend in agriculture to use biochar (BC) as a means for carbon storage and soil improvement, and it has been suggested, that feeding BC to livestock can improve animal health and performance, and reduce enteric methane emissions. The aim of this study was to investigate if adding BC to a balanced ration of a group of lactating Holstein dairy cows had an effect on their milk yield and quality, methane emission, nutrient digestibility and health. In a crossover experiment lasting for two 36-day periods, eight cows received their basal ration with and without 1 % DM BC. During the last week of each period, the cows were kept in tie stalls where milk yield and composition, feed intake and nutrient digestibility, as well as blood parameters were quantified. On the last two days, methane emissions were measured in respiration chambers. The results indicate that there was no significant effect of the addition of BC on any of the measured variables. Voluntary intake was not affected by the addition of BC (P=0.52) and none of the cows exhibited health problems in response to the treatment. There was no increase in milk yield (P>0.46) or composition (P>0.23) and methane emissions were not significantly affected (P>0.37). While the beneficial effects of feeding BC to animals suffering from health problems or receiving a poor diet cannot be excluded, the data of this experiment indicate that BC is not an effective feed additive to improve performance or reduce methane emission in dairy cows.

Coupled reduction in arsenic methylation and methanogenesis with silicate amendment in arsenic-enriched paddy soils

Methanogens play an important role in the demethylation of arsenic. Soil amendments that inhibit methanogens can increase dimethylarsinic acid (DMA), which is responsible for straighthead disease in rice. A decrease in methanogenesis caused by silicate fertilizer may increase DMA concentration in paddy soils and rice grains; the relationship between these two factors and their impacts on DMA concentration remains unclear. We applied silicate fertilizer (2 Mg ha−1) to japonica and indica rice grown on arsenic-spiked soils and found a simultaneous reduction in methane emissions and pore-water DMA concentration, compared to no-silicate fertilization. Gene and transcript copies of mcrA and arsM, as well as dominant methanogens and arsenic-methylating microbes decreased significantly with silicate fertilization. However, the sulfate-reducing bacteria and the gene and transcript copies of dsrB did not change significantly in response to the application of silicate fertilizer to paddy soils. The abundance of arsenic methylating microbes was significantly and positively correlated with the abundance of methanogens, but not with the abundance of sulfate-reducing bacteria. Methylomonas and Methylobacter, which harbor the arsM gene, were suppressed under silicate fertilization, suggesting that they have the potential to methylate As and play a crucial role in reducing pore-water DMA in As-enriched flooded paddy soils. Increasing Fe concentration, soil pH, and Eh value decreased pore-water DMA concentration, while decreasing arsenite concentration, arsM and mcrA gene abundance decreased it. While silicate fertilization decreased arsenite and DMA concentrations in pore-water, it had no significant effect on rice DMA content, but significantly decreased arsenite content. Results reveal that methanogens and arsenic-methylating microbes have a synergistic relationship under silicate fertilization that facilitates a significant reduction in methane emissions and DMA concentration in As-enriched paddy soils.

Mutation of rice SM1 enhances solid leaf midrib formation and increases methane emissions.

The leaf midrib system is essential for plant growth and development, facilitating nutrient transport, providing structural support, enabling gas exchange, and enhancing resilience to environmental stresses. However, the molecular mechanism regulating leaf midrib development is still unclear.In this study, we reported a rice solid midrib 1 (sm1) mutant, exhibiting solid leaf aerenchyma and abaxial rolling leaves due to abnormal development of parenchyma and bulliform cells. Map-based cloning revealed that SM1 encodes a litter zipper protein (ZPR). SM1 was mainly expressed in the sheaths and basal midrib and was associated with the nucleus. Further experiments indicated that SM1 can interact with OSHB1, preventing the formation of OSHB:OSHB dimers and subsequently repressing the expression of OSH1 involved in the regulation and maintenance of apical stem meristem formation. The sm1 mutant reduced long-distance oxygen transport ability from shoot to root. The impaired oxygen transport in the sm1 mutant may have contributed to the increase in methanogens and elevated methane emissions. Collectively, our findings revealed that the SM1-OSHB1-OSH1 modules regulate leaf aerenchyma development in rice. These modules not only enhance our understanding of the molecular mechanism of rice leaf aerenchyma development but also offer insights for reducing methane emissions through genetic modification.