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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]

Sustainable intensification (SI) is envisioned as an effective strategy for developing countries to increase farm productivity while reducing negative environmental and social externalities. The development of regionally appropriate SI options however requires accounting for the knowledge and preferences of key stakeholders. In Bangladesh, the Government has requested international donors to support the development of dry season rice expansion in the coastal region. Policies however tend to be made without adequate study of farmers' preferences and ambitions; this can render crop intensification efforts ineffective. Understanding farmers' preferences for alternative crops and crop management practices are therefore crucial for success where agricultural development investments aim at incorporating the principles of SI. Using coastal Bangladesh as a case study– we aim to (1) quantify farmers' preferences for alternative irrigated crop and crop management options in comparison to the status quo (land fallowing), (2) analyze whether farmers' preferences are conditioned by concerns regarding the cost and availability of irrigation and fertilizer inputs in comparison to expected net revenues, (3) understand how the heterogeneity in preferences can be attributed to farmer and/or farm characteristics, institutional, and biophysical factors, (4) determine how much farmers' are willing to invest in different crops and crop management options – including those reliant and not reliant on irrigation. Taking 300 farmers in two diverse coastal environments, a choice experiment (CE) was employed to explore the heterogeneity in farmers' preferences for different dry " rabi " season intensification options (' boro ' rice, maize, wheat and mungbean) against the status quo (dry season land fallowing after harvest of the monsoon season rice crop). Analyses included random parameter logit modeling followed by willingness-to-invest and profit simulations. Analyses revealed strong farmer preferences against rice and in favor of irrigated maize, and also in favor of rainfed or partially irrigated mungbean as an alternative to land fallowing. Irrespective of their location and environmental conditions, respondents had largely a negative preference for irrigation and fertilizer use due to high investment costs and associated production risks in the dry season. Nonetheless, a significant positive effect on their willingness-to-intensify cropping was observed where farmers felt it feasible to provide in-field drainage to limit waterlogging risks. The study signifies the importance of accounting for farmers' preferences while developing context-specific SI policies. Improving agronomic investments, tenure security, market, credit and extension support are likely prerequisites, alongside targeted diffusion of stress-tolerant mungbean and maize varieties for SI in coastal Bangladesh. Unlabelled Image • Government's policy encourages intensified cropping in the coastal region of Bangladesh. • Analyze farmers' preferences for alternative crop intensification options using a choice experiment. • Preferences against rice and in favor of mungbean, and maize as alternative to land fallowing. • Farmers' preference for non-rice crops in place of dry season land fallowing conflicts ongoing policy favoring rice. • Agronomic investments, tenure, markets, credit, and extension are prerequisites for sustainable intensification. [ABSTRACT FROM AUTHOR]

Coastal systems are facing natural and human-driven change coupled with a rising population. With increasing shifts in socioecological conditions during the past several decades, it is important to understand how socioecological drivers at different hierarchical levels: -micro, -meso, and -macro affect coastal farming systems, which play a crucial role in the livelihoods of coastal dwellers. Mixed rice-livestock-aquaculture farming in Southern Bangladesh exemplifies the rapid change occurring in many of the world's coastal farming systems in response to these drivers. We used panel data observations from the above study area and modeled trajectories of farm typologies, and the impact of multi-level socioecological drivers by a novel approach. Our approach integrates: (1) a well-articulated conceptual frame of change observed using (2) a temporal view of the potential drivers, change process and farm type outcomes, with the twenty years panel data of 502 households that is analyzed by means of (3) multivariate statistics in conjunction with panel data models that operationalize the conceptual frame. Our approach allows (a) estimating dynamic effects over time that typically cannot be estimated in a cross-sectional data set, (b) distinguishing between time-invariant fixed and time dependent random effects of multi-level socioecological drivers, and (c) controlling for omitted variables to a certain extent. Considering farming systems both within and outside of polder embankment systems intended to protect against oceanic water intrusion, we found a gradual shift from heterogeneous, rice-livestock farm types to more homogenous farms with less livestock and more off-farm activities. Micro-level factors including farm plot fragmentation, farmers' experience in cropping, machinery, salinity and soil fertility were influencing changes in farming systems. Meso-level factors including markets, road infrastructure, labor availability, access to extension and land tenure also affect the trajectory of farming systems change. Among macro-level drivers, increasing population density positively and significantly influenced cropping intensity among farms outside polder systems. Within polders, a positive but non-significant trend was observed for the influence of population density on cropping intensity. Our data also indicate negative and significant influence of cyclonic storms on cropping intensity over time in both areas. Our results underscore the importance of accounting for multiple levels of socioecological drivers of change when developing appropriate policy options for sustainable development in South Asia's coastal farming systems. • Agricultural changes in coastal Bangladesh over 20 years in response to external drivers. • Novel approach embedded in –micro–meso–macro modelling of trajectories of change. • Farming systems in Bangladesh show diverse complex spatio-temporal dynamics. • Heterogeneous, rice-livestock farms shifted to homogenous farms with off-farm income. • Effects of population pressure on cropping intensity are positive but inconsistent. [ABSTRACT FROM AUTHOR]

• Maize and wheat are proposed for diversification, but irrigation advice is limited. • Soil moisture content was above or near drained upper limit for depths below 0.5 m. • A significant effect of irrigation on yield was observed for maize only, in one year. • One irrigation, in addition to a starter irrigation, generally is sufficient to grow a crop. • Low-input maize cultivation is not always profitable and low fertilizer rates increase risk of negative returns. Further efforts are needed to combat poverty and agricultural productivity problems in the delta region of Bangladesh. Sustainable intensification of crop production through irrigation and production of cash crops such as maize and wheat might be a promising option to increase income and diversify food production. Only limited research has however been conducted on the potential of using surface water from canals as an irrigation source for maize and wheat production in the delta region. To better understand the contribution of shallow groundwater to crop production and number of irrigations needed for maize and wheat in this unique coastal environment, we conducted multi-locational trials on farmers' fields over three rabi seasons. In addition to soil moisture and salinity, we recorded the depth and salinity of the shallow water table throughout these experiments. Maize in particular requires considerable capital investment for seeds, fertilizer, irrigation and labor. Although farmers express wide interest in maize – which can be sold as a profitable cash crop into Bangladesh's expanding poultry feed industry – many of them are reluctant to invest in fertilizer because of the high entry costs. We therefore also investigated the profitability of growing maize under low and high (recommended) fertilizer regimens. Volumetric soil moisture at sowing and during the grain filling phase or at maturity indicated that there is ample supply of water in the profile. Most measurements were above the drained upper limit (DUL). We attributed this to the generally shallow water table depths, which never exceeded 2.75 m at any location, but generally stayed between 1–2 m depth throughout the season. The region's soil texture classes (clay loams, silt loams and silty clay loams) are all conducive for capillary rise of water into the rooting zone. Consequently, irrigation had a significant effect on maize yield in the driest winter only, whereas for wheat, it had no effect. The key for a successful maize and wheat production in the delta region of Bangladesh is to ensure a good crop establishment, which can be achieved with a starter and an additional irrigation at crown root initiation for wheat and at V6-8 for maize. Maize however is not always profitable. Compared to low fertilizer rates, higher rates reduced losses in low yielding site-years and increased profits in high-yielding site years. This indicates that it is advisable for farmers not to reduce fertilizer rates. Low-risk financial credit with rationally structured interest rates that allow farmers to invest in maize could potentially offset these constraints. [ABSTRACT FROM AUTHOR]

South Asia is the world’s most poverty-dense region, where climate change and climate variability are expected to result in increased heat stress and erratic precipitation patterns that affect agricultural productivity. Considerable evidence has been generated on the effects of these stresses on crop yield, though previous research has not yet examined their influence on the economic efficiency of cereal producers. Surveying 240 farmers across eight of Pakistan’s twelve agro-ecological zones, we examined the impact of temperature and precipitation anomalies – as indicators of climatic variability – and the number of days when temperature exceeds crop specific heat stress thresholds on the economic efficiency of rice and wheat production. To this end, we employed first-stage stochastic production frontier (SPF) models and second-stage ordinary least square (OLS) and quantile regression models. Both OLS and quantile regressions indicated that terminal heat >34 °C has a significant negative impact on wheat production economic efficiency. Small positive deviation (0.54 °C ± 0.16 SD) of the wheat season’s mean temperature from the medium-term historical mean also significantly and negatively affected economic efficiency across all regression models. Heat stress >35.5 °C during rice flowering in the monsoon also had a significant and negative impact. A slight positive deviation in temperature averaging 0.38 °C (±0.11 SD) above the medium-term mean also had significant negative effects across all regressions. Cumulative precipitation conversely had significant yet contrary effects, by offsetting farmers’ investment in supplementary irrigation and increasing economic efficiency. Our results highlight the fact that indicators of climatic variability and heat stress negatively affect the economic efficiency of both rice and wheat producing farmers. Farmers’ education and access to financial and extension services were however both positively associated with economic efficiency. Our findings point to the importance of developing interlinked agronomic, economic and socio-ecological policy strategies to adapt and increase the resilience of Pakistan’s cereal systems to climatic variability. [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]

Several studies estimate the immediate impact of climate change on agricultural societies in terms of changes in crop yields or farm income, though few studies concentrate on the immediate secondary consequences of climate change. This synthetic analysis uses a set of indicators to assess the repercussions of predicted income reductions resulting from climate change on food consumption, nutrition, health expenditure, education, and recreation in Zimbabwe, Cameroon, South Africa and Ethiopia. We also assess the potential decline in human development potential among smallholder dryland farmers in these sub-Saharan African countries. In contrast to previous efforts, the current study directly integrates the uncertainties in estimations of income changes and secondary consequences through a weighting scheme. The results reveal moderate to high levels of secondary impacts which could lead to increased vulnerability to diseases, susceptibility to nutritional disorders, deprivation of educational opportunities, and ultimately to a reduction in human and societal development potential among the considered nations. The article concludes by proposing a portfolio of policy options for ameliorating the secondary impacts of climate change in these sub-Saharan African countries. [ABSTRACT FROM AUTHOR]

Growing populations, changing market conditions, and the food security risks posed by rainfed cropping and climate change collectively indicate that Sub-Saharan African nations could benefit from transforming agricultural production to more intensive yet resilient and sustainable systems. Although highly underutilized, emerging evidence indicates that groundwater may be more widely available than previously thought, highlighting its potential role in facilitating such a transformation. Nevertheless, the possibility for such a transition is conditioned by number of complex factors. We therefore construct a transition index that integrates data considering groundwater and energy availability and cost, market access, infrastructural needs, farm conditions and natural resource stocks, labor availability, climate, population density, as well as economic and political framework variables, using a principal component analysis based methodology. Using the consequent multi-dimensional transition index and constituent intermediate indices, we provide an assessment of groundwater irrigation potential discussed in consideration of Burkina Faso, Ghana, Malawi, Ethiopia, Nigeria, Zambia, Namibia, Cameroon, and Zimbabwe. Our results, though preliminary, provide a methodology for conducting such an integrated assessment, while deriving a holistic set of policy options considering the transition towards appropriate use of groundwater for agricultural development. [ABSTRACT FROM AUTHOR]