Executive Summary

Sustainably managing limited resources, such as productive land areas and available freshwater, will be one of the world's most pressing challenges in the coming years. Population increases and economic growth will significantly influence humanity's future demand for land and water for different uses. In particular, changes in food and energy use will have substantial environmental impacts. They will also influence each other in many ways. At the same time, the production of food and energy, and the water resources they require, will be affected by global climate change. Sustainability issues arising from competition and synergies between future production of bioenergy and food, and related water use, are highly important in this context.

Population growth is one of the factors contributing to increased demand for land and water. While the world's population has approximately doubled since the 1960s, global economic activity has increased approximately 40 fold. Since growth in incomes is strongly correlated with increased consumption of animal-derived food (meat, milk, eggs), the combination of population increases and economic growth will likely result in increased feed and food production. This will drive up pressures on land and water resources if not counteracted by innovations that reduce land and water use. Social inequities are increasing as well, with both very rich and very poor populations often practicing ‘inefficient’ methods of using land and water.

Executive Summary

Buildings are key to a sustainable future because their design, construction, operation, and the activities in buildings are significant contributors to energy-related sustainability challenges – reducing energy demand in buildings can play one of the most important roles in solving these challenges. More specifically:

• The buildings sector and people's activities in buildings are responsible for approximately 31% of global final energy demand, approximately one-third of energy-related CO2 emissions, approximately two-thirds of halocarbon, and approximately 25–33% of black carbon emissions.

• Several energy-related problems affecting human health and productivity take place in buildings, including mortality and morbidity due to poor indoor air quality or inadequate indoor temperatures. Therefore, improving buildings and their equipment offers one of the entry points to addressing these challenges.

• More efficient energy and material use, as well as sustainable energy supply in buildings, are critical to tackling the sustainability-related challenges outlined in the GEA. Recent major advances in building design, know-how, technology, and policy have made it possible for global building energy use to decline significantly. A number of lowenergy and passive buildings, both retrofitted and newly constructed, already exist, demonstrating that low level of building energy performance is achievable. With the application of on-site and community-scale renewable energy sources, several buildings and communities could become zero-net-energy users and zero-greenhouse gas (GHG) emitters, or net energy suppliers.

Recent advances in materials and know-how make new buildings that use 10–40% of the final heating and cooling energy of conventional new buildings cost-effective in all world regions and climate zones.

Executive Summary

Bioenergy has a significant greenhouse gas (GHG) mitigation potential, provided that the resources are developed sustainably and that efficient bioenergy systems are used. Certain current systems and key future options including perennial cropping systems, use of biomass residues and wastes and advanced conversion systems are able to deliver 80 to 90% emission reductions compared to the fossil energy baseline. However, land use conversion and forest management that lead to a loss of carbon stocks (direct) in addition to indirect land use change (d+iLUC) effects can lessen, and in some cases more than neutralize, the net positive GHG mitigation impacts. Impacts of climate change through temperature increases, rainfall pattern changes and increased frequency of extreme events will influence and interact with biomass resource potential. This interaction is still poorly understood, but it is likely to exhibit strong regional differences. Climate change impacts on biomass feedstock production exist but if global temperature rise is limited to less than 2°C compared with the pre-industrial record, it may pose few constraints. Combining adaptation measures with biomass resource production can offer more sustainable opportunities for bioenergy and perennial cropping systems.

Biomass is a primary source of food, fodder and fibre and as a renewable energy (RE) source provided about 10.2% (50.3 EJ) of global total primary energy supply (TPES) in 2008. Traditional use of wood, straws, charcoal, dung and other manures for cooking, space heating and lighting by generally poorer populations in developing countries accounts for about 30.7 EJ, and another 20 to 40% occurs in unaccounted informal sectors including charcoal production and distribution.