The role of biomass and biowaste in the green energy transition of islands and an introduction to the μgas-to-grid concept

The green transition of the energy sector in islands has always been a challenging task. The connectivity of islands with the (mainland) central grid can be problematic, especially when the distance is significant. In such cases, isolated electrical grids need to be developed on the islands, and the most common fuel of choice has historically been diesel/ fuel oil. On a second level, diesel/ fuel oil is also used for the heating of buildings. In European Union, a green energy transition is underway and renewable energy systems are increasing their overall fraction in the total energy mix, with wind and solar (variable renewable energy systems) being the ones with the highest added installed capacities. It should be denoted that isolated grids have stability issues when variable renewable energy (VRE) systems are integrated. This present study analyzes the case of Lesvos island and presents the opportunities that are available for the case of biomass and biowaste utilization in this green energy transition. The seasonal availability of pruning from olive trees and liquid biowaste, i.e. cheese whey wastewater (CWW) and olive mill wastewater (OMW), have been assessed for the island and a thorough survey of the operating production facilities in the island has been implemented and will be presented. On the one hand, pruning from olive trees can be gasified and a gasification modeling case will be presented (MAGSY model). On the other hand, liquid biowaste can be anaerobically digested for the production of biogas and the methane potential of each type of liquid biowaste has been measured. Energy production from biomass/ biowaste can assist the grid stability during a green transition to higher VREs utilization, since a “gas-battery” can be always be available and can cover any shortages. Finally, the idea of μgas-to-grid will be presented, where different biomass sources will be converted into gaseous fuels and injected into a small natural gas grid. The idea of the μgas design would consist of the local small-scale conversion of biomass/ biowaste into gaseous fuels and the centralized upgrade of the gases before the injection to a small natural gas grid. This idea can assist the second level of energy transition, when the isolated island grids will be connected to the central grids but the demand for greener fuels for heating in buildings or for the transportation sector will have to be addressed. This study will discuss the crucial role that biomass can play in both two levels of energy transition.