Environmental assessment of a small power plant based on palm kernel shell gasification

Abstract

A small power plant based on biomass gasification technology is attractive to provide electricity to many remote areas without fossil fuel access because biomass is locally available and contributes to net-zero carbon emissions in the terms of a greenhouse gas component. Palm kernel shell is a potential biomass in Indonesia to provide energy needs. It is available in scattered areas that are economical for a small-scale power plant operation up to 200 kW. The gasification technology converts the shell into combustible gases, which are also known as producer gases with carbon monoxide and hydrogen as the main components for fuelling a gas generator set resulting in carbon dioxide and water in the flue gas. Although palm kernel shell considered carbon-neutral, a power plant based on biomass gasification also emits CO2 indirectly as a result of the fossil fuel combustion during shell generation in a palm oil mill, handling and transportation from the mill to the power plant. A power plant based on the palm kernel shell gasification system produces greenhouse gases and solid residue as char and tarry components in the producer gas. This assessment examined the global warming potential level of a 5-kW power plant based on palm kernel gasification technology using a Gate-to-Gate approach to develop system improvement scenarios. All carbon dioxide emissions were predicted with an openLCA database of Environmental Footprint (MID-point indicator). The mass and energy balance calculations resulted in the amount of generated char. A laboratory experiment was conducted to observe tar content in the producer gas. It was found that the power plant emits 1.69 kg CO2 eq/kWh, produces 0.33 kg char/kWh and the producer gas contains 2.70 × 10−4 kg tar/kWh. It is recommended that when using palm kernel gasification for electricity generation, plant managers should consider char as a solid conditioner in a palm plantation area and implement a tar removal system to minimize gas genset failure.