**3. Soil impacts of modern bioenergy programs**

Soils are a critically important, basically non-renewable ecosystem resource, that provide the physical, biological, chemical, and hydrologic foundation for agricultural and forest bioenergy feedstocks production [36–38]. Soils are able to redevelop after being degraded but the


**Black** = direct physical effect, **Green** = effect mediated through the crop specific attributes such as root or canopy structure, **Blue** = effect is both physical and plant -mediated

**Table 1.** Interdependencies of water and soil resources (adapted from [2]).

**2.4. Organic residues**

118 Energy Systems and Environment

**2.5. Algae**

mal feed and bedding) are considered.

**2.6. Electrical generation impacts**

has decreased from 15 m<sup>3</sup>

cling of process water.

Secondary and tertiary waste biomass (e.g. municipal wood waste, food processing waste, manures, and wastewater with high organic content) has the potential to improve water quality in communities by reducing landfill deposits, and leachates. However, utilization of this resource remains inefficient. Even with zero landfill policies and a Waste Framework Directive, the EU-28 countries recovered energy from only 7% of its non-recyclable municipal waste in 2011 [32]. Currently, use of primary waste biomass (e.g. harvest residues, forest thinnings, and slash) for energy is limited because of the economics of transporting these residues. Increased use of wood residues can improve land and water productivity but requires that site-specific conditions (e.g., soil, climate topography, etc.) and competing uses (e.g., ani-

The water impacts of algal propagation vary widely by technology and environmental conditions, with water use ranging from minimal up to 3,650 L L−1 of biodiesel or advanced biofuel produced [33]. Freshwater is needed to replace water losses from open ponds, even when halophilic organisms are used. While the volumes in photobioreactors are relatively small, cooling requirements, usually met by freshwater, are large. Water impacts of conversion tech-

In general, water impacts of biomass powered electricity generation remain similar to fossil fuel pathways, with large water withdrawals but low consumptive use ranging from 0–1800 L MWh−1 [34]. Cooling water, which may contain some salts, is returned at higher temperature to the source stream or basin, with variable ecological impact. Water requirements for biofuel processing continue to improve. Use per tonne of feedstock has decreased dramatically for both corn and sugarcane ethanol. For instance, the consumptive water use of ethanol-sugar mills in Southeast Brazil

However, in water stressed regions new or expanded facilities may still not be approved due to the associated water demand [35]. While, untreated effluent can create water quality problems, process water offers an opportunity to recover and recycle nutrients. Biofuel facilities with zero liquid discharge have been operating in the U.S. since 2006 and continue to expand worldwide. Technological improvements in water recovery and recycling have progressed to the point that some facilities are able to use municipal wastewater and some have achieved closed loop recy-

Soils are a critically important, basically non-renewable ecosystem resource, that provide the physical, biological, chemical, and hydrologic foundation for agricultural and forest bioenergy feedstocks production [36–38]. Soils are able to redevelop after being degraded but the

Mg−1 of sugarcane bagasse prior to 2008 to <3 m<sup>3</sup> Mg−1 in 2008 [35].

nologies result from competition from often scarce freshwater supplies.

**3. Soil impacts of modern bioenergy programs**

time period might be several centuries or millenia, depending on climate and vegetation. Because of this long time factor, soils are considered to be non-renewable. They are heterogeneous and highly diverse components of ecosystems that form over long time periods under the influence of parent mineral material, climate, landscape position and biological activity.

As the base of bioenergy production systems, soils constitute a major factor that interacts with water to determine the type and amount of plant biomass production (**Table 1**, [2]). They provide the physical anchor which tie plants to the earth, supply water and mineral nutrients for plant growth, decompose and recycle organic material and residues and mediate hydrological processes [39–41]. Bioenergy feedstock systems are part of agricultural and forest management systems that provide multiple ecosystem products and services [42]. These include plant biomass, water flow, water quality control, biodiversity, cultural heritage, and carbon storage. Soils are important factors in each of these services. Therefore, it is critical that in the process of managing soils for bioenergy production, soils must be managed to sustainably provide a wide range of ecosystem services important to human communities. Maintaining the quality of soils will ultimately ensure maintenance of water quality.
