Optimization of Renewable Energy Deployment for NbS

One of the most important aspects of NbS research is the study of the linkage between environmental conservation and various benefits. For example, the analysis of the carbon sequestration function of forests for the social issue of climate change mitigation is a typical example. In fact, the IUCN has identified climate change as one of the key issues to be addressed in NbS. However, while the basic concepts and examples of the role of nature conservation in climate change adaptation have been summarized in, for example, debates of EbA, they have not been sufficiently examined in the context of climate change mitigation. In particular, elucidating the trade-offs that certain NbS approaches can make with climate change mitigation, for example, can provide insights into the formulation of integrated policy packages.

The study presented here is based on this concern and examines measures to optimize renewable energy and NbS in Japan. The nature of energy policy has an impact on the lives of citizens through land use planning and other means. In this study, a model called REROUTES was developed for energy optimization, and a series of policy processes were proposed to give policy implications to the model. The schematic is as follows.

The first step is a workshop with citizen participation. Policies related to the introduction of renewable energy can have a significant impact on the lives of citizens. Therefore, it is necessary to start by qualitatively drawing up a future vision that includes new values and necessary policies through citizen participation workshops. In such workshops, the method of backcasting is used. This is a method of thinking often used in the context of realizing a sustainable society, in which the desired future image of the region is set and then the necessary procedures are identified. The energy demand and CO2 emissions that would result from the realization of this future vision are calculated for each industrial sector using the ExSS model on a regional scale.

The next step is to optimize the energy mix using the Renewable Energy Optimization Model (REROUTES). The outline of this model is as follows. First, by optimizing the renewable energy mix based on the assumption of future energy demand, a series of changes in land use related to renewable energy production are evaluated from changes on the social side. The renewable energies to be optimized in the REROUTES model are solar energy, wind energy, small and medium-sized wind energy, hydropower, geothermal energy, and biomass-derived energy, which are subdivided into 267 types according to their scale and form, and the amount of their introduction becomes an explanatory variable. The evaluation indicators for the renewable energy mix are (1) renewable energy self-sufficiency, (2) economic balance, (3) CO2 specific reduction, (4) waste biomass resource recycling rate, (5) ecological impact area, and (6) renewable energy species diversity index.

In addition, this study proposes a process to combine multiple methods for ecosystem management, including the type and amount of renewable energy, natural regeneration of abandoned land, and forest management, and to quantify which combinations can avoid negative impacts on biodiversity and ecosystem services and maximize synergies. Through the process described above, it is proposed to organically link the qualitative elements of the future vision of society desired by citizens and the model of renewable energy optimization. Such research is an example of how NbS can be effectively applied to society.

This kind of research is necessary for the actual implementation of NbS into policy. This is the first attempt to apply NbS to the process of introducing renewable energy in Japan, but the choice of energy mix is important in developing countries as well, and it may be useful as a reference.