Abstract The feasibility of commercial-scale cocomposting of waste biomass from the control of invasive Acacia species with pine bark waste from the lumber industry, in a blend ratio of 60:40 (v:v), was investigated and compared to previous research on the composting of Acacia without additional feedstock, to determine the potential process and end-product quality benefits of cocomposting with bark. Pile temperatures rose rapidly to >70 °C and were maintained at >60 °C for several months. Acacia and bark biomass contained a large fraction of mineralisable organic matter (OM) equivalent to approximately 600 g kg(-1) of initial OM. Bark was more recalcitrant to biodegradation compared to Acacia, which degraded at twice the rate of bark. Therefore, incorporating bark increased the final amount of compost produced compared to composting Acacia residues without bark. The relatively high C/N ratio of the composting matrix (C/N = 56) and NH3 volatilisation explained the limited increases in NH4(+)-N content, whereas concentrations of conservative nutrient elements (eg P, K, Ca, Mg, Fe) increased in proportion to OM mineralisation, enriching the compost as a nutrient source for horticultural use. Nitrogen concentrations also increased to a small extent, but were much more dynamic and losses, probably associated with N volatilisation mechanisms, were difficult to actively control. The physicochemical characteristics of the stabilised end-product, such as pH, electrical conductivity and OM content, were improved with the addition of bark to Acacia biomass, and the final compost characteristics were suitable for use for soil improvement and also as horticultural substrate components.