Quantification of Biomass Production Potentials from Trees Outside Forests—A Case Study from Central Germany

Abstract

Woody biomass of trees outside forests (TOF) is gaining increasing interest in many countries as it is a renewable energy source that has not been managed for bioenergy production. Our case study describes two independent approaches to assess regional area of TOF as a means for the biomass production potential of TOF within a study region in Germany, the Gottingen district (area: 1,118 km2): (1) a statistical sampling with field inventory data, and (2) an area-wide GIS-mapping approach based on open-access aerial imagery. For our particular study, the differences between the mapping-based approach and the sample-based approach were minor (sampling: 24.37 ha and 16,670 t of dry wood per year with a relative standard error 11.6 % vs. area-wide mapping: 24.35 ha and 16,055 t; standard error not available). Due to a minor difference of only 3.7 % between the two approaches, we conclude that area-wide mapping serves as a sound basis for a quantification of bioenergy potentials from TOF. It also shown that only about 62 % of all TOF objects (74 % of the total annual biomass production) would be directly accessible via the existing road infrastructure (without heavy machinery). In terms of available end-use energy, the regional biomass potential translates to an annual amount of 233 TJ which, in turn, reflects only about 0.9 % of the annual end-use energy demand in the study area. This marginal contribution to the region’s energy supply is due to the fact that TOF covers only around 24 km2 (~2 %) in our study area.