Biomass and waste co-firing in industrial energy systems is a growing technology that is in an early stage of deployment in the UK. Typical power station projects are utilising biomass at a ratio of up to 10% coal replacement by mass. In cement kiln applications, biomass is derived primarily from waste materials and is only being co-fired at less than 10% replacement in the UK. There are a number of technical issues currently impeding the large-scale uptake of this low-carbon combustion methodology. This paper examines the current state of the art for biomass co-firing and introduces some of the issues surrounding this technology. Characterisation of the feedstocks is key in understanding the combustion behaviour when the material is co-fired in large-scale utility boilers. A number of candidate energy crops and wastes were characterised for combustion behaviour and ash properties. The results showed that, although there is a large variation in the materials selected for the study, there is a comparatively small variation in the properties of the varieties of energy crops.