It's August on a small Aegean island. The tavernas are full, every air conditioner is running, and somewhere near the harbour an old diesel power station is working flat out, burning fuel that arrived by tanker. On many Greek islands that aren't connected to the mainland grid, this is still how the lights stay on. It's expensive, polluting and exposed to every swing in oil prices.
What if part of that energy came from what the island already has: olive pits, vine prunings, grape marc and farm waste? That's the idea behind biomass microgrids. Let's look at how they work, what they can and can't do, and how island communities can make them happen.
Why islands need a different energy model
Non-interconnected islands generate their own electricity, mostly with diesel or heavy fuel oil. This costs far more than power on the mainland. In Greece, the gap is largely covered through the Public Service Obligations (ΥΚΩ) charge that every consumer pays on their electricity bill. In other words, island diesel is a cost the whole country shares.
Undersea cables are gradually connecting more islands to the mainland grid, but for many small and remote islands that won't happen soon, or at all. For them, the answer is local renewable energy in a microgrid: a small, smart electricity network that can run on its own.
What a biomass microgrid is
A microgrid is a local network that combines generation, storage and smart control to supply a community, either connected to a larger grid or fully independent. Solar and wind are usually the backbone. The problem is that they don't produce on demand: no sun at night, no wind on calm days.
This is where biomass fits in. Unlike solar and wind, a biomass unit is dispatchable: it can produce power whenever needed, as long as there's fuel. Combined with solar panels, wind turbines and battery storage, it can fill the gaps and reduce reliance on diesel backup.
The technologies: how biomass becomes power and heat
| Technology | Suitable feedstock | What it produces | Note |
|---|---|---|---|
| Anaerobic digestion | Wet waste: olive mill wastewater, manure, food waste | Biogas (mainly methane and CO₂) for engines; digestate as fertiliser | Works at 35–55°C with microorganisms |
| Gasification | Dry biomass: wood chips, prunings, olive pits | Synthesis gas (CO, H₂, CH₄) for engines | High temperature, needs careful gas cleaning |
| Combustion with CHP | Dry biomass, pellets | Electricity and heat together | Most mature technology |
| Biomass boilers | Pellets, olive pits, wood chips | Heat only (buildings, hot water, district heating) | Simple and widely used |
The key is combined heat and power (CHP). Small biomass plants typically turn only around a quarter to a third of the fuel's energy into electricity. Recovering the heat for hotels, public buildings, greenhouses or hot water raises total efficiency dramatically.
What the island already has: local biomass
Greek islands have more biomass than you might think:
- Olive pits and pomace from olive mills,
- Olive mill wastewater, a polluting waste that is ideal for anaerobic digestion,
- Vine and olive prunings, which are often burned in the open,
- Grape marc from winemaking,
- Livestock manure,
- Organic waste from hotels and restaurants, especially in summer.
Using these residues solves two problems at once: it produces energy and reduces waste that would otherwise pollute soil and water.
The benefits for island communities
- Energy security: less dependence on fuel shipments and on oil price spikes.
- Lower emissions: when biomass comes from residues and is managed sustainably, its emissions are much lower than diesel. It isn't automatically "carbon neutral", though. That depends on where the feedstock comes from and how far it travels.
- Waste management: agricultural and organic waste becomes a resource instead of a problem.
- Local jobs and income: collection, processing, operation and maintenance stay on the island.
- Community ownership: through energy communities, residents can share in the benefits.
Greek islands leading the way
Greece already has some of Europe's best-known island energy projects, even if most rely on sun, wind and batteries rather than biomass:
- Tilos: the EU-funded TILOS project combined a wind turbine, solar panels and a large battery system in a hybrid microgrid, becoming a European reference for island energy autonomy.
- Astypalea: a partnership between the Greek state and Volkswagen is turning the island into a model for electric mobility powered by renewables.
- Chalki: a solar park supplies the island's public buildings and residents, as part of a "green island" initiative.
- Agios Efstratios: a long-planned hybrid renewable project aims to make the island one of the first in the Aegean to run largely on clean energy.
Biomass is the missing piece in many of these models: it can supply power and heat in the evening and in winter, when solar is weakest.
The challenges
- Steady feedstock: agricultural residues are seasonal, so storage and a reliable collection system are needed.
- Technical support: gasification and digestion units need skilled operators and fast access to spare parts, which is hard on remote islands.
- Upfront cost: small biomass plants cost more per kilowatt than solar, so funding and good design are essential.
- Air quality: combustion must use modern filters to avoid local pollution from particulates.
- Permitting: licensing can take a long time, which discourages smaller projects.
How an island community can get started
- Map local resources: how much biomass, from where and in which months.
- Form an energy community: in Greece, Law 4513/2018 allows citizens, local authorities and businesses to set up energy cooperatives.
- Start with solar and storage: it's the fastest and cheapest step, and biomass can be added for evenings and winter.
- Use the heat: plan CHP alongside heat users such as hotels, schools or greenhouses.
- Look for funding: EU programmes, national development funds and the EU's Clean Energy for EU Islands initiative can support studies and investment.
Frequently asked questions
Is biomass energy carbon neutral?
Not automatically. Biomass from residues that would otherwise rot or be burned in the open has a low carbon footprint. Cutting forests for fuel or transporting biomass long distances can cancel out the benefit.
Can a biomass microgrid fully replace diesel?
Combined with solar, wind and batteries, it can cover a large share of an island's needs. Most projects still keep a backup generator for emergencies.
What's the difference between biogas and syngas?
Biogas comes from anaerobic digestion of wet waste and is mainly methane and CO₂. Syngas comes from high-temperature gasification of dry biomass and is mainly carbon monoxide and hydrogen.
The takeaway
Islands are where the energy transition is most visible: expensive diesel on one side, abundant sun, wind and farm waste on the other. Biomass microgrids won't solve everything, but alongside solar, wind and batteries they can turn local waste into power and heat, cut costs and keep value on the island.
Does your island have untapped biomass, such as olive mills, vineyards or farms? Share this article with your local council or energy community, and read about green infrastructure as a natural shield against CO₂. For the terms you came across, check our CO₂ Term Glossary.