Sustainable cost-effective residential heating with biomass-based oil An EU-funded initiative produced and tested bio oil residential heating systems from agricultural and forestry residues and developed a compatible combustion boiler. Energy © Koldunov Alexy, Shutterstock Residential heating systems can play an important role in making Europe’s energy system clean, secure and efficient. Most renewable biomass resources, however, are solid materials with low energy density; even the most advanced residential heating systems have difficulty handling the inconsistent properties of biomass from agricultural and forestry residues. The Residue2Heat project addressed this challenge, utilising sustainable, ash-rich biomass and residues in residential heating applications (from 20 kWth to 200 kWth) to provide sustainable heat at a competitive price. “We aimed to replace the large quantities of fossil and first-generation biofuels currently used with biomass residue streams unsuitable for food or feed production, and thus have a low impact on indirect land use change,” says project coordinator Herbert Pfeifer. Consortium members converted biomass residue streams via fast pyrolysis, which heats organic material in the absence of oxygen, into a uniform, second-generation liquid biofuel called fast pyrolysis bio oil (FPBO). In addition, researchers tailored existing residential heating systems to allow the use of FPBO. Innovative technology The FPBO has about 70 % of the energy content of the biomass and around half the heating value of a conventional fuel oil. “The first challenge was to produce FPBO – despite its wide range of possible biogenic raw materials – with consistently high-quality and highly standardised physico-chemical properties. The second challenge was to adapt a highly efficient condensing heating system for the use of FPBO, since the FPBO properties differ from those of conventional fuels,” Pfeifer explains. Project partners employed innovative, fast-pyrolysis technology to convert high-ash biomass residues like wheat straw, forest residue, bark, miscanthus and clean wood into liquid biofuel for residential heating. Residue2Heat used fundamental modelling and experimental research to adapt parts of existing residential heating systems, such as burner components, to the use of FPBO. This lab-scale burner was scaled up to a combustor suitable for residential heating systems. “A demonstration of FPBO usage in a residential scale heater included the stable combustion of FPBO, prolonged burner operation times (greater than 100 hours) and start-stop operation. Furthermore, the unit was operated and monitored in the actual intended environment for Technology Ready Level 5,” notes Pfeifer. Lower emissions Fuel properties were tailored for residential heating throughout the course of the study, resulting in a high-quality, standardised FPBO. Researchers tested typical components used in heating systems, such as pump and fuel nozzles, for their FPBO compatibility. Pfeifer observes: “Since information on FPBO spray and combustion is limited in the scientific literature, both were analysed at a fundamental level to support the lab-scale burner development.” Residue2Heat’s main outcome was the development of stand-alone, small-scale residential boilers (between 20 kWth and 60 kWth) fuelled by FPBO. Additional achievements include the production of high-quality FPBO from high-ash-biomass residues, atomisation and combustion of FPBO, design and manufacturing of modified burner components and a logistics plan for storage and handling. Sustainability chain evaluation of various FPBO types (based on feedstock) showed emission savings of 80 % to 94 %, meeting greenhouse gas emission saving requirements of 60 % and 70 % of the Renewable Energy Directive (RED) and RED2, respectively. “In addition, the ashes derived from the FPBO production process have potential for providing nutrients for soil ecosystems, and could therefore be used for agricultural applications," Pfeifer concludes. Keywords Residue2Heat, fast pyrolysis bio oil (FPBO), residential heating, biomass, agricultural, forestry residue, boiler, Renewable Energy Directive
