Bioenergy production on degraded and marginal land

Current global energy supply is primarily based on fossil fuels and is widely considered to be unsustainable. Bioenergy is considered an important option in making future global energy more sustainable. However, increasing global trade and consumption of bioenergy in industrialised countries has been accompanied by a growing concern about the environmental, ecological, and social impacts of (modern) bioenergy production. But producing bioenergy on degraded or marginal land may avoid many of the negative effects because this land is considered to be largely unsuitable and often economically unattractive for agricultural crop production. Despite its potential advantages, the use of degraded and marginal land for bioenergy production has its own drawbacks that may limit its economic attractiveness and diminish its sustainability. The most important challenges are related to its difficult growing conditions and often being an important resource for poor rural communities, particularly those with no formal land rights. While these challenges are acknowledged in many studies, little is actually known about the implications for the technical and economic potential and the economic performance of bioenergy production on degraded and marginal land. Therefore, this thesis assesses the technical and economic potentials, economic performance, and environmental impacts of bioenergy production on degraded and marginal land. Five chapters evaluated bioenergy production on degraded and marginal land for different settings and at different geographical scales. Chapters 2 and 3 focused on palm oil production in Malaysia and Indonesia. These chapters assessed the use of Imperata grasslands as an alternative to tropical rainforest or other land types. Chapter 4 evaluated cassava ethanol, jatropha oil, and fuelwood production from marginal semi-arid and arid land in eight sub-Saharan African countries because these regions have been under-researched and have substantially different conditions and requirements for bioenergy production than more humid regions. Chapters 5 and 6 investigated woody bioenergy production from salt-affected land focussing on a global scale (Chapter 5) and on local and national scales in Bangladesh, India, and Pakistan (Chapter 6). Salt-affected land is important to study because of its widespread occurrence globally and the difficulties it poses for agricultural production. Three main conclusions can be drawn from this thesis. Firstly, bioenergy production on degraded and marginal land has a substantial potential for contributing to global energy consumption (approximately 18% of current global primary energy consumption). Secondly, the analysis of economic performance suggests that bioenergy production on these land types can in many cases be competitive with other bioenergy sources and even fossil fuels. Thirdly, perennial bioenergy production on degraded and marginal land can have both positive (e.g. carbon sequestration, improvements in soil fertility, and reduction in soil degradation) and negative (e.g. exacerbation of water shortages in water-scarce regions) environmental impacts; more research is needed to determine the conditions under which bioenergy production results in negative environmental impacts so that these can be avoided or at least minimized