One of the examples is the Verdo Power Plant (previously Energi Randers) that went for being a 100% coal-fired CHP plant to being able to use 100% biomass. Read more about this here.
Biomass is a renewable and carbon-neutral energy source, and as such it is the sustainable alternative to fossil fuels. There is a strong political desire to implement renewable energy supply in many countries. This has led to economic incentives for biomass-based energy generation. These incentives vary from country to country and also vary over time in the individual countries.
The emission in particular of SO2 and NOx are generally lower for biomass than for fossil fuels. Therefore a biomass conversion of a fossil fuel-fired power station can reduce or even eliminate the cost of complying with current and future legislation.
An additional advantage is that a biomass conversion allows older units to operate for an extended period under conditions that are both profitable and environmentally sound.
Existing coal-fired boilers can be converted to biomass firing. This requires a modification of the fuel-handling and preparation system as well as an evaluation of the boiler suitability and any necessary modifications to the combustion system. In most cases original fuels can be maintained and this increases boiler fuel flexibility
To obtain more information about fossil fuel to biomass conversion :