The finite nature of fossil fuels and the emission of greenhouse gases as result of the consumption, these resources provide the impetus to seek alternative sour­ces of clean energy, which can be produced in a sustain­able manner. This important quest underpins the essential requirement for research and development on various types of bioenergy. Bioethanol production has been the focus of considerable research in the context of liquid fuels for transportation. The use of starch — based (first-generation) agricultural products as substrates as bioethanol feedstocks is possible but raises some concerns because of potential competition with food production. Although numerous investigations on bioenergy have been performed over the past decades to clarify the potential of, and to develop processes for the use of agricultural crops and biomass as feedstock for fuel and energy, the recent period has seen a renewed intensity of research on biomass to bio­energy conversion technologies and processes, with the aim of developing economical and sustainable solutions at commercial scale. To support economic sustainability, biorefinery systems have been implemented to convert renewable materials, such as wood or agricultural crops, into additional valuable products such as platform and feedstock chemicals, and pharma compounds. It is envisaged that the biorefinery concept should enable a transition from the traditional fossil fuel-based plat­forms for production of commodity products to more environmentally favorable and sustainable bio-based processes. For researchers and industrialists alike, the biorefinery approach brings both significant scientific and technical challenges and much opportunity for tech­nological innovation.

Second-generation bioenergy uses the lignocellulose present in woody biomass, forestry residue, agricul­tural residues, food wastes, agricultural wastes and animal wastes. Agricultural residues include the straw from wheat and rice, sugar cane bagasse, stem and roots from food crops, the top ends of trees like euca­lyptus not used in paper manufacture, and fast devel­oping tall grasses (e. g. Miscanthus spp., coastal grasses, etc.). A detailed understanding of the compo­sition of the lignocellulosic waste is essential to develop and optimize mechanistic models for its conversion. Inclusion of pretreatment processes to aid the integration of waste streams into the raw materials for ethanol plants in such models is essential to increase both fuel (ethanol)/bioenergy yields, recover valuable coproducts and biorefinery feedstocks, as well as to reduce process costs. Hydrolysis of lignocel — lulosic materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. Hydro­lysis using enzymes (generally derived from microbial sources) is the preferred option as enzymes can be used to selectively convert carbohydrate-rich biopoly­mers in biomass to fermentable sugars, without forma­tion of by-products that inhibit downstream bioenergy and biorefinery conversion processes. However, pretreatment of the lignocellulose to reduce its recalci­trance to enzymatic and microbial conversion is essen­tial. Pretreatment by physical, chemical or biological means is an essential process for ethanol production from lignocellulosic materials. Pretreatment also enhances the biodegradability of the wastes for ethanol and biogas production and increases accessibility of the enzymes to the biopolymers present in the biomass/waste feedstocks. Research is necessary to improve process efficiencies in the areas of pretreat­ment and bioconversion, and to explore new technolo­gies for conversion of lignocellulose to bioenergy. Similarly, the major challenge for microalgal biodiesel production is the high cost of producing microalgal biomass, and the current significant environmental, safety and sustainability concerns surrounding the recovery and extraction of lipid fractions used for bio­diesel production. In this sector, the key issues to be solved are the costs for harvesting the algae, protection of the high-oil microalgae from the contamination by other algae, and the development of environmentally and operationally more benign extraction processes. Another important issue for both lignocellulosic ethanol and microalgal biodiesel processes involves the development of technologies for the utilization of coproducts and residues formed through primary bioconversion processes which should increase overall process economics. Utilization of each fraction in biomass agricultural wastes provides an effective way to minimize environmental pollution, address food security problems and improve agricultural waste management approaches.

This book focuses on current innovative methods and technological developments which are aimed at over­coming the bottlenecks in biofuel and bioenergy processes. Reviews of the potential of lignocellulosics for the production of (bio)chemicals are also included. Chapters on biorefining routes resulting in a product with higher market value than ethanol have been included. It is envisaged that once such approaches have reached viable commercial scale, global depen­dence on petroleum for a host of products used in day-to-day applications will be reduced, and a more sustainable global bioeconomy will result.

Editors

Foreword

Our present industrial civilization relies on the consumption of enormous amounts of energy and much of today’s economic wealth is based on a petro­leum-based economy. Petroleum not only is used as energy in transport but also is the starting material of many other products of our daily life including such diverse products as plastics, pharmaceuticals, solvents, fertilizers, pesticides and clothing up to the tarmac, which we use for the transport of these products. However, our continued reliance on fossil fuels will make it impossible to reduce greenhouse gas emissions to stop environmental problems such as global warm­ing. Without decisive actions, the global usage of energy and energy-related emissions of carbon dioxide is pre­dicted to double by 2050. Although there is an active debate when the demand for oil will exceed its supply (Peak Oil), it is clear that our present economic system will need a major shift to develop effective alternatives including a more sustainable economy. This sustainable development will be based on renewable energy and biomass sources as well as more efficient ways to use these.

Traditionally, biomass has been used to produce food, feed and wood fiber. But biomass can also provide energy in the form of (bio)fuels and it can be used as a source of feedstock chemicals replacing the petro­leum-based products. The development of such a bio­based economy is occurring already at a relatively rapid pace and some of its products are already on the market including first-generation biofuels. The commercial viability of this approach will depend largely on the availability of cost-competitive technologies capable of converting (waste) biomass within a holistic concept of a biorefinery to biofuels and other bio-based products. Biorefining—the sustainable processing of biomass into food/feed ingredients, chemicals, materials and bioenergy—aims to use the available biomass resources as efficient as possible. At the moment, a wide range of biomass conversion technologies are under develop­ment to improve efficiencies, lower costs along the whole supply chain and improve the environmental performance. But there is also a need for further techno­logical innovation leading to more efficient and cleaner conversion of a more diverse range of feedstocks. These include not only existing lignocellulosic waste residues from forestry, agriculture and urban communities but also the generation of new feedstocks from energy crops or microalgae. A first wave of cellulosic biofuels demon­stration plants is now reaching completion producing transportation fuels from agro-, forestry and process residues. To make the overall process more market competitive, these plants co-produce added-value bio­based products thereby supplying processes that are less energy or chemically intensive compared to their petroleum-based counterparts.

Increasing deployment of biomass will include also other challenges for our society including an increasing competition for land, questions of biodiversity and soil quality or the availability of water resources. But biomass will be an important part of the future energy mix thereby contributing to a low CO2 future. Excluding biomass from the energy mix would significantly increase the cost of decarbonizing our energy system.

This book has been initiated to describe the current stage of knowledge on bioenergy research from various perspectives, thereby outlining also those areas where further progress is needed.

Dr. Bernhard Seiboth

Professor, Head of Molecular Biotechnology, Vienna University of Technology, Vienna, Austria