**5. Conclusions**

Water and soil are so closely linked that the assessment of positive and negative effects of bioenergy production on water and soils should be part of any integrated analysis considering the environmental, social, and economic dimensions of bioenergy production. Water footprints and other measures have little informative value unless combined with data about resource availability and measures of competing uses at similar spatial and temporal scales. Assessment of the relative positive or negative soil and water effects of bioenergy systems depends largely on whether changes in management of land, water and other resources for bioenergy development alters the state and quality of soil and water [44].

Forest and agricultural bioenergy systems that utilize accepted BMPs should be capable of maintaining soil quality and high-quality water. Excessive removal of plant material from the field or forest may jeopardize soil and water quality. Extended or intensified cultivation of plant annual crops for bioenergy feedstock will produce the same impacts as when the objective of crop cultivation is for food. Cultivation of perennial grasses and woody plants commonly causes less impact on water and soil resources. These production systems can, through well-chosen siting, design, management and system integration help mitigate potential soil and water problems associated with current or past land use. Ultimately, careful land management through the implementation of BMPs will improve soil and water use efficiency.

Advances in water recovery and recycling have the potential to reduce water requirements for conversion processes as well as contribute to the reduction of manufacturing effluents. Feedstock production and conversion stages can, in some cases, be integrated to use resources more effectively and support good land and water management.

The quantity and timing of water withdrawals should be carefully considered in context of water needs, watershed vulnerability, and resilience to disturbance of hydrological cycles. Water scarcity may limit some conventional bioenergy systems in some regions. However, other bioenergy cropping systems may be able to take advantage of currently non-conventional water sources.

Matching bioenergy feedstocks, management practices, and conversion technologies to local conditions and constraints is essential for development of sustainable bioenergy systems. Successful implementation requires investments in the development of suitable plant varieties and conversion systems, systems integration to use resources effectively, and implementation of BMPs in forestry and agriculture.
