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Strategies to counter bush encroachment Potentials of bush-biomass

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In Namibia, 3% bush biomass is added every year at the expense of savannah biomes or pastures, a total of about 1.3 million hectares. Assuming 10 tonnes of biomass p. ha., which can be extracted in an absolutely environmentally friendly and sustainable manner, 13 million tonnes of biomass are available each year from the increase alone. Only a minimal  part of this would be needed for the partnership with Hamburg. With a withdrawal of up to 13 million tonnes, the overall system is sustainable. The expected demand for Hamburg is significantly lower.

Wood pellets made of black thorn Wood pellets made of black thorn (Senegalia mellifera), [heating value around 5 MWh/kg]

Potentials of bush-biomass

A change in land use through the extraction of biomass from the encroached areas can lead both to increased release and to increased binding (sink) of greenhouse gas emissions (GHG) in the overall balance. This depends on the answers to the questions: What follows the thinning of the bush biomass? What happens to the soil organisms and to the soil itself? What is the subsequent land use?

Namibia is extremely affected by climate change and is a country of adaptation to climate change. The bush encroachment together with the increasingly unpredictable rainfall already leads to a substantive change in land use, which massively affects different groups of people and endanger the livelihoods of the many small farmers. It also affects the country's biodiversity and water balance (e.g. Goengroeft, A. et al (2018))1.

At the same time, however, the progressive bush encroachment also results in a large sink for carbon dioxide bound in woody biomass. The restauration of savannah landscapes through the removal of bush wood  should not negate this effect but should be carried out together with the preservation of the sink function for GHG. Currently, there are various  greenhouse gas scenarios for the different land-use options, which vary from the development of an additional sink for GHG to the massive release of GHG. The  partnership with Hamburg clearly prefers such land-use scenarios which maintain or reinforce the lowering effect. For this purpose, customised mixed forms of land use must be developed. This is to be achieved in cooperation with the planned biomass industrial parks in Namibia which will provide the corresponding expertise and logistics options.

The aim is to combine existing expertise with the experience of field practitioners. The aim is to enter a bioeconomy with as much cascading benefits from the existing biomass as possible. A developed land-use option harvests the bush biomass and then keeps the land free for 4 to 6 years in order to re-develop a savannah landscape. For this purpose, the stick rashes (shoots that grow from the sawn-off stump) are actively managed. The resulting product can be used as an animal feed additive and partially replace feed imports to Namibia or also enable export. There are currently three options for the emerging grass: cattle pasture, wild land pasture (game farming) and material use (e.g. grass paper). After the 4 - 6 years, the harvest is stopped on these areas and the bush can regrow. These additional usage options will be further explored in parallel in a collaborative research project.

If Namibia is to succeed in the balancing act between adaptation to anthropogenic climate change and the important conservation or restoration of the GHG sink (climate protection/decarbonisation) from a global point of view, progress must be made consistently on new forms of land use. The Hamburg-Namibia Biomass Partnership intends to make a significant contribution to this.

Processing of bush wood in Namibia

So far, bush wood has been primarily harvested by hand and on a small scale. This applies in particular to the use of firewood and export charcoal. When it comes to large quantities, special harvesting machines are used, which until now have been operated only by a few specialised harvesting companies.

The plan is now to build up biomass industrial parks (link to details "Biomass Industrial Parks"). For the supply of these parks, the harvest will be carried out by manual, semi-mechanised and fully mechanised processes.

During the machine harvest in the bush encroached areas, wood chips are produced immediately. After transporting to the biomass industrial parks which are between 50 and 100 km away from the harvest area, the wood  chips will be processed into wood pellets. The energy for this processing step is to be generated directly in the park via photovoltaics.

Wood pellets have the advantage of a higher calorific value per kg mass compared to wood chips, which means that they require significantly less loading space during transport. As a result, CO2 transport emissions and costs per calorific value are lower. In addition, the production (i.e. the refinement of raw wood to the product pellets) would generate the greatest possible added value on site.


1 Goengroeft, A.; de Blßecourt, M.; Classen, N.; Landschreiber, L. & Eschenbach, A. (2018). Acacia tress modify soil water dynamics and the potential groundwater recharge in savanna ecosystems. Climate change and adaptive land management in southern Africa – assessments, changes, challenges and solutions (ed. By R. Revermann, K.M. Krewenka, U. Schmidel, J.M. Olwoch, J. Heimschrot and N. Jürgens), pp. 177 – 186. Klaus Hess Publishers, Göttingen & Windhoek.

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