Environmental Engineering Reference
In-Depth Information
6
Ecologically Sustainable
Bioenergy Cropping Systems
Species Selection and
Habitat Considerations
Christopher R. Webster and David Flaspohler
Michigan Technological University
Steve Pawson and Eckehard Brockerhoff
New Zealand Forest Research Institute
contents
6.1 Introduction ............................................................................................................................ 99
6.1.1 The Mirage of a Bioenergy Panacea......................................................................... 100
6.2 Defining Ecological Sustainability ....................................................................................... 102
6.2.1 Key Terms and Processes ......................................................................................... 103
6.2.1.1 Nutrient Cycling ......................................................................................... 103
6.2.1.2 Biomass and Trophic Structure .................................................................. 103
6.2.1.3 Vegetation Diversity and Structure ............................................................ 103
6.2.1.4 Species-Area Relationships........................................................................ 104
6.3 Bioenergy Cropping Systems and Species Selection ............................................................ 104
6.3.1 Residues .................................................................................................................... 104
6.3.2 Bioenergy Plantations and Dedicated Crops/Trees .................................................. 106
6.3.2.1 Implications of Changing Crop Rotation Lengths ..................................... 106
6.3.2.2 System Stability and Landscape Considerations ....................................... 108
6.3.3 Native versus Exotic Species .................................................................................... 109
6.3.3.1 Case Study: Exotic Conifers as Biofuel Crops and Invasive Weed Risks ......... 110
6.3.4 Perennial Polycultures .............................................................................................. 111
6.4 Other Considerations ............................................................................................................ 111
6.5 Toward a Diverse Bioenergy Portfolio ................................................................................. 112
References ...................................................................................................................................... 112
6.1 IntroductIon
Bioenergy at its most fundamental level is about burning the accumulated proceeds of photosyn-
thesis. Fossil bioenergy, in the form of coal, fueled the early industrial revolution and today, along
with oil, sustains contemporary human civilization. In the early 20th century, these concentrated
and conveniently packaged fossil fuels largely replaced wood, tallow, and dung as sources of heat
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