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Liquid biofuels are considered as a strategy for achieving energy security, stimulating rural development and mitigating climate change. Low-income countries largely focus on biofuel production from non-food crops and trees grown on underutilized lands, in order to minimize food, fuel and environmental trade-offs. Unfounded claims on the potential of such alternative biofuel crops led to large-scale investments, especially in jatropha (Jatropha curcas) monoculture plantations. Productivity and economic outcomes proved to be poor, however, which subsequently led to a global downturn in research and investment, leaving the potential of other species and approaches unexplored. In Chapter 1, we hypothesize that agroforestry-based approaches that carefully integrate a mix of native biofuel tree species into the existing farming system, offer unique opportunities in comparison with jatropha monocultures, including limited risk, increased by-product valorization, and expanded ecosystem services provision. This PhD study aims at evaluating the bio-economic potential of agroforestry-based biofuel systems by quantifying three critical success factors: farmer perception and adoption, oilseed yield, and economic impact. The in-depth empirical analysis is based on a mature agroforestry-based biofuel program in Hassan district, South India. Since 2007 this program stimulates the cultivation of native oilseed tree mixtures on farms through a range of extension and implementation activities.In Chapter 2 we assess farmer perception and adoption of oilseed trees and the biofuel value chain in Hassan district. To this end, cross-sectional survey data of 396 farm-households in Hassan district are collected. We find that although 60% of the farmers cultivate oilseed trees, oilseed collection rates are generally low (13%), as are oil expeller use (<1%) and biofuel marketing (<1%). To examine the impact of the biofuel program on adoption, we use regression analyses addressing various forms of selection bias. We find that various activities of the biofuel program stimulate oilseed tree cultivation but not oilseed collection. Low seed prices, high opportunity costs of labour, and value chain underdevelopment are major factors impeding households to collect seeds from planted or wild oilseed species.In Chapter 3 we use a labelled choice experiment to assess the same farmers' preferences for alternative production systems, value chain organisations and market developments. This allows predicting the extent to which hypothetical changes in these characteristics could change the likelihood of adoption. Our results demonstrate that biofuel programs can benefit from ex ante analyses to improve their design. We find that most farmers (71%) are likely to adopt biofuel trees in most scenarios, especially species with relatively high yields, low labour requirements and high oilseed prices. Nevertheless, value chain reorganization through contracting and labour provision proves to be the key lever to stimulate adoption. This calls for further research on effective contract design and implementation, and for developing alternative business models.Chapters 2 and 3 indicate that pongamia (Millettia pinnata) is the species with highest adoption potential. However, yield levels and dynamics of this undomesticated species remain poorly understood, despite of the fundamental role they play for its biofuel potential. In Chapter 4 we address the critical lack of scientific evidence by collecting primary seed and oil yield data from 81 pongamia trees in South India, and explore which factors might determine yields using empirical models. Our results indicate that annual seed and oil yields for pongamia trees vary widely, but generally remain below 2500 kg/ha and 1000 liter/ha, respectively. This current field performance is substantially lower than commonly reported figures in the literature. Furthermore, our results suggest that a complex interplay between genotype, environment and agronomy leads to large spatiotemporal variation in yields, and that this interplay remains poorly understood. Long-term yield monitoring is required to get better insights into yield mechanisms, and to assess the actual potential of pongamia as a reliable and significant source of biofuel feedstock.In Chapter 5 we address common methodological shortcomings in the literature on profitability of novel biofuels, by developing a sound framework for quantifying the long-term financial performance of agroforestry-based biofuel value chains. The framework is applied to calculate profitability of pongamia cultivation and processing in Hassan district. The results show that pongamia cultivation has limited financial potential, and is only profitable in small-scale settings, in the middle to long term and for a subset of farmers. If biodiesel is envisaged as the end product, the value chain requires substantial fiscal and marketing support to be economically viable. For current prices, financial performance is much higher if the seed oil is marketed instead of processed to biodiesel. These findings are case-specific, while the developed framework opens the door to comprehensive investigation of the financial performance of other oilseed tree species and in other regions.The interdisciplinary framework allows concluding that the potential of agroforestry-based biofuel systems as sources of energy, income and employment is currently very limited. The program in South India succeeds as an agroforestry program but not as a biofuel program. Low profitability impedes local farmers to collect oilseeds, while processors have no financial incentive to convert oil to biodiesel. We find that similar challenges pertain to small-scale agroforestry systems as to jatropha-based plantation systems, although the former are a Low-Risk High-Diversity approach to build feedstock for the future. The wider validity of our findings should be further explored to determine in which niches alternative biofuel crops may still have potential.

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On the first of January 2019, new European regulations concerning maximum Cadmium (Cd) concentrations in chocolate came into effect. It is to be expected that these regulations will impact the different stakeholders in the cocoa industry. Agronomic research in different regions of Ecuador demonstrated the occurrence of various high Cd concentration zones. Since Ecuador exports about 30% of its cocoa to the European Union, the new EU regulations might affect Ecuador’s cocoa industry. In light of this, a survey-instrument was developed to collect and study socio-economic data on Ecuadorian cocoa farmers. In order to assess the magnitude of the possible impact of the new regulations, the value of cultivating cocoa to the Ecuadorian farmer was estimated. This estimation was performed by including a contingent valuation section in the survey. The estimated value of cultivating cocoa to the Ecuadorian cocoa farmer was estimated at US$ 4,249 per hectare with two explanatory variables, namely gender and stated importance of cultivating cocoa being significant. This amount was then extrapolated to a nationwide value of the cultivation of cocoa in Ecuador of US$ 2,251,970,000. To put the calculated figure into perspective, this value corresponds to the value of 3.17 years of Ecuador’s cocoa exports. Based on our sample, 71 percent of this figure can be attributed to smallholder cocoa farmers. Finally, as to safeguard the reputation and quality of the Ecuadorian cocoa industry, a policy-making measure to compensate all farmers situated in high Cd zones in order to stop producing cocoa and switch to cultivating other crops was proposed. Our calculations suggest a one-time cost of US$ 1,013,386,500 combined with a yearly cocoa export loss of US$ 319,500,00 to implement this policy. This measure could possibly prevent a potential total economic loss up to US$ 2,251,970,000. The latter would occur in a worst-case scenario where all cocoa-importing countries stop importing cocoa beans that are produced in Ecuador.

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Nigeria's annual maize (Zea mays L.) production has increased from 2.4 million metric tons in 1961 to about 10.4 million metric tons in 2013 which placed Nigeria as the 11th largest producer of maize in the world. However, yield levels have remained very low and far below the potential of the crop. Aside water, soil nutrient depletion and poor nutrient management have been reported to be one of the most important abiotic constraints contributing to a stagnant low yield of maize in Nigeria. Therefore, to optimize the productivity of maize in Nigeria, evaluation of site-specific nutrient-related constraints reducing yield and viable ways to counteract such constraints become imperative. A minimum of 90 on-farm nutrient omission trials (NOT) will be conducted in three states of Nigeria falling within the maize belt in the Nigerian Savanna ecological zone. The nutrients content in the soil (prior to the establishment of the NOT) and in the plant tissue will be analyzed. Viz-à-viz agronomic and yield data will also be taken. The data generated will be used for the determination of nutrient limitations and balances using Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND). An algorithm for the determination of nutrient requirement to achieve an optimal yield will be evaluated using Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS). At the end, as a follow-up, demonstration of adapted fertilizer advices will be installed and evaluated by farmer groups and extension services.

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Maize is an important staple food and feed crop widely grown in Sub-Saharan Africa (SSA). However, the yield of maize is often below the best yield that can be obtained on-farm with current technology. Specifically in Nigeria, the average yield of maize was 1.8 tons/ha in 2014 compared to the world average of 5.6 tons/ha which indicates a maize yield gap of 3.8 tons/ha. Thus, there is the need for intensification of maize production through the use of innovative approaches to close the maize yield gap in Nigeria and SSA at large. To close the attainable yield gap of the smallholder maize-based farmers' using innovative approaches geared towards increasing their maize productivity and income, improving their food security and addressing the challenge of rural poverty, a Bill and Melinda Gates Foundation (BMGF) supported project known as Taking Maize Agronomy to Scale in Africa (TAMASA) is developing decision support tools for nutrient and crop management amongst other products and services of the project in Nigeria, Ethiopia and Tanzania. One of the decision support tools of particular interest to this doctoral research project is known as Nutrient Expert (NE) decision support tool. The tool is meant for use by extension service providers in generating fertilizer recommendations for specific fields or growing environments of maize-based farmers' which will help increase their maize yield and produce positive welfare benefits. Beyond the geospatial soil and agronomic research inputs in the tool development, a socioeconomic research is necessary to accompany the development, evaluation and dissemination process of the tool. This doctoral research includes an ex-ante and an ex-post components and focuses on both farmers'(ultimate beneficiaries of the tools) and extension agents' (target users of the tools) in order to effectively bridge the knowledge gap necessary for the successful uptake and continuous utilization of NE decision support tools. The ex-ante component seeks to obtain empirical information on preferences and behavioral responses (choice behavior) of farmers' and extension agents' to NE decision support tools through implementing choice experiment for farmers' and extension agents'. The ex-post component aims to empirically establish the potential of the tools in enhancing fertilizer use, yield and income of maize farmers' through implementing a randomized controlled trial.