| dc.description.abstract | Bioenergy, currently the largest source of renewable energy, is expected to play an important role in the future energy mix. However, its large scale use can also have adverse impacts when looking at a broader sustainability perspective, including expansion of cropland resulting in (indirect) land use change. This can be avoided by using underutilised degraded land to grow dedicated bioenergy crops, because this type of land is usually unsuitable and economically unattractive for food crops. Moreover, perennial crops such as short rotation woody crops (SRWCs) could provide different ecosystem services.
A possibility to unlock the potential of degraded land might come in the form of the Bonn Challenge. The Bonn Challenge is a global effort to restore 150 million hectares (Mha) of deforested and degraded land by 2020 and another 200 Mha by 2030. Although bioenergy is not the main objective of the Bonn Challenge, growing bioenergy crops could provide extra economic incentives and possibly additional greenhouse gas emission mitigation by replacing fossil fuels. In a first rough global estimate, the SRWC potential from the Bonn Challenge was estimated to be between 33 and 67 EJ yr-1, assuming that the total restoration area of 350 Mha would be used for bioenergy crop production (IRENA 2016a).
However, some key factors were not considered in determining this potential: local conditions were not taken into account and an average yield was assumed for all regions. Furthermore, it does not show for which countries growing bioenergy crops could be interesting in their restoration strategy. Therefore, keeping in mind both the opportunities and risks posed by bioenergy from degraded land, it is important to give a more accurate estimate of the bioenergy potential in context of the Bonn Challenge. The present study seeks to address this need by estimating the sustainable potential from restoration pledges made to the Bonn Challenge. The focus is on Sub-Saharan Africa, which is considered a leading continent due to the large number of pledges from Sub-Saharan Africa countries.
Two analyses were done. First, the biomass potential for all 18 pledges in Sub-Saharan Africa was estimated using the area pledged by each country as input. This analysis used a geographic explicit method as summarised in Figure A. Scenarios were used to provide insight in the impact of key uncertain factors on the total potential. The scenarios (step 3, Figure A) were used to see the effect of different management strategies a country could use to restore their pledged area. They varied in the share of the pledge used for SRWC plantation and in the location that is used: either the use of land with a high yield (Resource focused), a high degree of degradation (Restoration focused) or a high degree of degradation while excluding agriculture (Restricted) was prioritised.
The findings of this analysis are shown in Figure B. If all pledges are completely used for bioenergy production (Resource scenario), the potential of SRWCs is estimated to be 6.01 EJ yr-1. However, a restoration strategy as considered in the Resource scenario is considered infeasible. The scenarios a) using a lower share of the pledges and b) focussing on the use of land with a high degree of degradation are thought to give more realistic estimate of the potential. They still result in substantial potential of 0.20-1.85 EJ yr-1. Congo and Congo DRC are estimated to have the highest potential, while Benin and Niger have a very low potential.
Next to the Sub-Saharan Africa analysis, a more detailed country level analysis was conducted for Rwanda and Kenya. This analysis used studies on the potential areas suitable for restoration and the potential restoration options on these areas. The results show that Rwanda has a potential of 45 PJ yr-1 on 1.4 Mha when the restoration strategy as proposed by the ROAM assessment is executed. Kenya has a potential of 28 PJ yr-1 on 2.2 Mha. This method could be applied to other countries once their ROAM assessments have been completed.
From the present study, it is clear that bioenergy could contribute substantially to the Bonn Challenge by providing additional economic benefits and sustainable biomass supply. The underlying principle behind the initiative, forest landscape restoration, includes restoration activities in which cultivation of perennial bioenergy crops could be envisioned. Sustainable bioenergy production could give a boost to the Bonn Challenge, by providing extra economic incentives and possibly additional greenhouse gas emission mitigation by replacing fossil fuels. Depending on the strategy used for restoring the pledged area, the bioenergy potential could be substantial. The restoration strategy will be completely depended on the goals and opportunities in each country. Conducting studies on a country level is therefore necessary in order to provide a more detailed potential. Incorporating this in future ROAM studies is an interesting option, as these studies involve engagement with local stakeholders.
When the original estimate (33-67 EJ yr-1 on 350 Mha) is converted to the 75.4 Mha assessed in the present study, this yields a potential of 7.1-14.4 EJ yr-1. The results of the present study show that this estimate is likely too high. Using more detailed data in a future study could reduce the range of potential further. | |
