Biomass in Regional and Local Context
Bio-resources offer the possibility to transform carbon dioxide, water, and nutrients, with the help of solar irradiation, into valuable material products. Primary terrestrial bio-resources include crops, forage and wood, which can be utilised directly as food, feed, construction material, energy sources or as a starting point of conversion chains that may lead to biofuels and a wide variety of chemicals. A coarse estimate on the base of FAO data puts current production of crops at roughly 6 billion t/yr  and global production of wood at 3.8 billion mVyr.- The wide range of use and, in particular, the central role for human nutrition leads to brisk demand and competition for bio-resources. Although they are renewable in the sense that, given sustainable care for forests, grass laud and fields, they may be harvested again after every cultivation cycle, then annual yield is restricted by the finiteness of then basic resource, namely fertile land.
It is this bond to land that makes terrestrial bio-resources contextual. Solar irradiation as the driving force of plant growth requires area for its conversion to useful services, regardless if it is assimilation of water and carbon dioxide to organic compounds or its transformation to electricity by photovoltaic panels. So, all resources and sendees based on solar irradiation are inherently de-ceutralized and area bound. Bio-resources are no exceptions to this rule but are particularly inefficient resources when assessed according to their conversion rate of solar energy to useful energy content. According to Zhu et al. (2008), maximum theoretical conversion rates of solar irradiation into bio-resources are between 4.6% for C-3 plants like wheat, and 6% for C-4 plants like maize. Practical conversion rates are lower, usually around 50% of these theoretical values. This compares to conversion rates of 15—20%3 for PV panels and even higher efficiencies for thermal solar collectors.
The low conversion rate of solar irradiation into bio-resources clearly assigns them then role within efforts to manage carbon emissions. A range of environmental Life Cycle Assessments (LCA) based on either Global Wanning Potential (GWP), e.g., Schlomer et al. (2014), or on aggregated assessment methods, like the Sustainable Process Index (SPI), see Kettl et al. (2011a), show consistently that all renewables-based energy technologies perfonn substantially better in ecological tenns than all fossil- based technologies, but that bio-energy performs worse than all other renewables-based competitors. Bio-resources are, however, material products with a much broader spectrum of applications than just providing energy sendees. This spectrum ranges from providing food and feed to industrial bio-products.
like paper, timber and a large variety of bio-chemicals to storable energy carriers. Rational use of bio-resources, therefore, favours their use as food, feed and material products. Their role within energy provision should be focussed on applications that require material energy carriers, such as bio-fuels for transport or for pror iding heat or electricity when no other renewable energy can be used.
The area to capture solar irradiation is, however, only one factor in the generation of bio-resources. Yields of bio-resources are critically dependent on soil quality and climate. Water and nutrients are also indispensable resources whose availability and quality are critically dependent on the spatial context, as are soil quality and climate. Together these factors define what crops may possibly be cultivated in a certain region.
Finally, cultivated laud must be seen within its cultural, economic and social context: Yield of crops is critically dependent on the know-how of fanners as well as their economic ability to purchase farm equipment and auxiliary production means, such as fertilisers and pest control. This explains why there is a wide range in yields per hectare and year for crops in different locations, even for the same crop, e.g., the yield for maize varies from 6.6 t/ha.yr for Albania to 9.9 t/ha.yr for Austria and 11.1 t/ha.yr for the U.S. The regional economic and industrial structure will also influence what crops are cultivated and how they are utilised. Infrastructure such as roads, railways, transport grids for gas and electricity as well as heat distribution grids are further essential spatial factors to market bio-resources and sendees and products derived from them. This chapter will discuss how utilisation technologies for bio-resources are influenced by their spatial context, what properties are critically important for optimal value chains based on bio-resources and what guides the structure of regional utilisation technology networks.
-  See https://news.energysage.com/what-are-the-most-efficient-solai-panels-on-the-market/ [last accessed April 2019].
-  Data from FAO statistics for 2017, see http://www.fao.Org/faostat/en/#data/QC [last accessed April 2019].