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Tar formation is one of the major problems during biomass gasification due to blocking and fouling processes in engines and turbines. Downstream gas cleanup process and conditioning are required to eliminate tar issues. For this reason, methods to reduce tar formation inside the gasifier are gaining more attention. In this work, a novel design for an inclined nozzle and a combustor was proposed and tested in a low-tar biomass (LTB) gasifier to evaluate the effect on tar reduction. The design process was based on a swirling flow created by an inclined nozzle that allows good mixing between pyrolysis gases and gasifying air. The swirl combustor created large internal annular and reverse flow zones with the help of swirl flow. Thus, the combustor had a positive effect on the combustion of the mixture of air and pyrolysis gases and induced thermal cracking in the partial oxidation zone. Recycling ratio (recycle gas/air, v/v) and combustion degree of volatiles were used to evaluate the performance of the inclined nozzle and combustor. The result showed that the tar yields in pyrolysis and partial oxidation zones were on average 1693 mg/Nm3 and 255 mg/Nm3, respectively which accounted for a reduction of 86.6% and 12.7% tar compounds in these zones, respectively. Besides, the producer gas leaving the gasifier had a tar content below 1%, and measured tar content was 7.4-27.14 mg/Nm3 for the tested biomass with moisture contents of 9–34%. Tar removal efficiency was found on average 84.9% after passing the pyrolysis gas through the partial oxidation zone, whereas tar in the producer gas was removed with an efficiency of 99.1% at the gas outlet zone. At an equivalence ratio of 0.35, the new design had the optimal performance with a recycling ratio of 0.35 and combustion degree of volatiles of 98.6%. The achieved producer gas could be directly fed to an internal combustion engine or a gas turbine at small to medium level power generation in remote rural off-grid areas. [Display omitted] • Inclined nozzle and combustor are introduced to reduce tar content of the producer gas (7.4 mg/Nm3). • Tar removal efficiency due to the effect of an inclined nozzle and combustor was 99.1%. • Recycling ratio and combustion degree of volatiles are key parameters of performance evaluation. • About 87% of tar compounds combusted in the partial oxidation zone by swirl flow effect. • Less than 1% tar content is observed at the gas outlet zone. [ABSTRACT FROM AUTHOR]

Diversification of smallholder rice-based cropping systems has the potential to increase cropping system intensity and boost food security. However, impacts on resource use efficiencies (e.g., nutrients, energy, and labor) remain poorly understood, highlighting the need to quantify synergies and trade-offs among different sustainability indicators under on-farm conditions. In southern coastal Bangladesh, aman season rice is characterized by low inputs and low productivity. We evaluated the farm-level impacts of cropping system intensification (adding irrigated boro season rice) and diversification (adding chili, groundnut, mungbean, or lathyrus) on seven performance indicators (rice equivalent yield, energy efficiency, partial nitrogen productivity, partial potassium productivity, partial greenhouse gas footprint, benefit-cost ratio, and hired labor energy productivity) based on a comprehensive survey of 501 households. Indicators were combined into a multi-criteria performance index, and their scope for improvement was calculated by comparing an individual farmer’s performance to top-performing farmers (highest 20%). Results indicate that the baseline system (single-crop aman season rice) was the least productive, while double cropped systems increased rice equivalent yield 72–217%. Despite gains in productivity, higher cropping intensity reduced resource use efficiencies due to higher inputs of fertilizer and energy, which also increased production costs, particularly for boro season rice. However, trade-offs were smaller for diversified systems including legumes, largely owing to lower N fertilizer inputs. Aman season rice had the highest multi-criteria performance index, followed by systems with mungbean and lathyrus, indicating the latter are promising options to boost food production and profitability without compromising sustainability. Large gaps between individual and top-performing farmers existed for each indicator, suggesting significant scope for improvement. By targeting indicators contributing most to the multi-criteria performance index (partial nitrogen productivity, energy efficiency, hired labor energy productivity), results suggest further sustainability gains can be achieved through future field research studies focused on optimizing management within diversified systems. [ABSTRACT FROM AUTHOR]

Large changes have taken place in smallholder farming systems in South Asia's coastal areas in recent decades, particularly related to cropping intensity, input availability, climate risks, and off-farm activities. However, few studies have investigated the extent to which these changes have impacted farm-level crop productivity, which is a key driver of food security and poverty in rainfed, low-input, rice-based systems. The objective of this study was to conduct an integrated assessment of variables related to socioeconomic status, farm characteristics, and crop management practices to understand the major factors influencing crop productivity and identify promising leverage points for sustainable development in coastal Bangladesh. Using a panel survey dataset of 32 variables from 502 farm households located within polder (coastal embankment) and outside polder systems during 2005–2015, we employed statistical factor analysis to characterize five independent latent factors named here as Farming Challenges, Economic Status, Crop Management Practices, Asset Endowment, and Farm Characteristics. The factor Farming Challenges explained the most variation among households (31%), with decreases observed over time, specifically households located outside polders. Individual variables contributing to this factor included perceived cyclone severity, household distance to main roads and input-output markets, cropping intensity, and access to extension services. The most important factors for increasing crop productivity on a household and per unit area basis were Asset Endowment and Crop Management Practices, respectively. The former highlights the need for increasing gross cropped area, which can be achieved through greater cropping intensity, while the latter was associated with increased fertilizer, labor, and pesticide input use. Despite the importance of these factors, household poverty trajectory maps showed that changes in off-farm income had played the strongest role in improving livelihoods in this coastal area. This study can help inform development efforts and policies for boosting farm-level crop productivity, specifically through agricultural intensification (higher cropping intensity combined with appropriate and efficient use of inputs) and expanding opportunities for off-farm income as key pathways to bring smallholder households out of poverty. [ABSTRACT FROM AUTHOR]

Rice cultivation in the Northwestern Indo-Gangetic Plains (IGP) of India is often associated with high energy use, calling into question its sustainability. We applied a bootstrapped meta-frontier with a truncated regression to a database of 3,832 rice farms from the input-intensive rice production tracts of the Northwestern IGP as part of an assessment of energy use efficiency aimed at identifying entrypoints for more sustainable and efficient practices. District-specific technical efficiency score ranged between 0.68 and 0.99, with a mean of 0.86–0.90, suggesting an average potential for improvement in energy use efficiency of 10–14% within each district. Observed mean meta-frontier technical efficiency scores ranged between 0.60 and 0.81. On average, energy use efficient farms had 42% or higher energy use efficiency in the districts of Ambala, Fatehgarh Sahib, and Karnal. In contrast, in other districts efficient farms had 5-19% higher energy use efficiency than the inefficient farms. Higher rates of tillage, irrigation, and fertilizer application were identified among inefficient farms, with patterns of energy use efficiency varying to some extent between study districts. Both efficient and inefficient farms in Kapurthala and Ludhiana exhibited similar patterns of energy for tillage and land preparation, whereas the energy output from both efficient and inefficient farms were similar in Kurukshetra. These data suggest that in order to improve the efficiency of energy use in rice farms in the Northwestern IGP, district-level policy interventions and incentives might be required. The methodological approach and evidence provided in this study may be of use to identify pathways toward sustainable energy use in other intensively managed rice production landscapes in other countries. Similar analyses that employ meta-frontier and truncated regression approaches can be carried out for other performance indicators, for example profitability and carbon footprints, to explore and identify management and policy interventions to assist farmers to more appropriately utilize scarce and costly resources. [Display omitted] • Energy input – output data for 3832 farms used for energy-use efficiency assessment. • Bootstrapped data envelopment analysis and truncated regression identified energy-use efficiency drivers. • Mean district-specific technical efficiency score was 0.86–0.90 • Focusing on crop management is more important than socio-economic factors. • Policy planning should focus district wise inefficient rice production practices. [ABSTRACT FROM AUTHOR]