Pelleting Invasive Environmental Weed Biomassfor Sustainable Bioenergy Production

Abstract

As global efforts toward net-zero emissions accelerate, the demand for renewable solid bioenergy—particularly pelletised biomass—is rapidly increasing. Invasive environmental weeds (IEW), which generate large but underutilised volumes of green waste, present a promising yet underexplored resource for bioenergy production. This study evaluates the feasibility of converting IEW into market-grade solid biofuels through pelletisation. A selection of woody and non-woody species was characterised for lignocellulosic composition and processed under a matrix of temperature (25–100 °C) and pressure (50–150 bar) conditions. Key physical and chemical attributes of the pellets were assessed. Non-woody species such as Brazilian Nightshade and Climbing Asparagus, containing approximately 24% lignin, yielded pellets with high durability (97.3–98.3%), elevated calorific values (18.8–19.2 MJ/kg), and low ash content (2.9–5.1%), meeting market standards for solid biofuels. Similarly, woody species such as Easter Cassia met these benchmarks. In contrast, species like Singapore Daisy and Mexican Ruellia exhibited high ash content (11.1–36.5%) and elevated levels of nitrogen, sulphur, potassium, sodium, and silicon—factors that may affect combustion performance and emissions. Surface-response modelling was used to identify optimal pelleting conditions, while principal component analysis revealed the key parameters influencing feedstock suitability. These findings demonstrate that, under appropriate processing conditions, IEW biomass can be effectively valorised as a renewable energy source. Addressing challenges related to ash chemistry and unit density—potentially through co-pelleting or additive integration—could further enhance the role of IEW in diversifying Australia’s biofuel supply chain and supporting the transition to low-emissions energy systems

Keywords: Carbon Neutrality, Climate Change Mitigation, Lignocellulosic Biomass Densification, Net Zero Transition, Renewable Solid Bioenergy