Abstract Energy demands of a cassava starch plant (CSP) were investigated and modeled. Four combined heat and power (CHP) systems using biogas were evaluated and compared, including energy self-support, economic feasibility and environmental impacts. Assessment results indicated that CHP system with reciprocating internal-combustion engine (ICE-CHP) and micro turbine (MT-CHP) can meet all the energy demands of the CSP. ICE-CHP technologies obtained the best profit, followed by MT-CHP, B/T-CHP and common system. The four systems are economically feasible, ICE-CHP showed better economy than MT-CHP system. Both ICE-CHP and MT-CHP systems have the lowest environmental impacts comparing to other CHP systems in view of emissions. ICE-CHP should be suggested firstly considering the short payback period (4.57 year), the lowest environmental impacts and 100% of energy self-support. Boiler/Turbines CHP (B/T-CHP) will not be adopted as it is unable to supply all the electricity needs of the CSP. Plant availability shows the greatest impact on the payback period. If the investment cost of MT-CHP decreases by more than 12.7%, MT-CHP would have better economy than ICE-CHP. The results are helpful for the management of CSP to select the suitable CHP technology.