A pilot-scale low-emission boiler system consisting of a bio-fuel boiler and plasma-chemical hybrid NOx removal system is investigated.This system can achieve carbon neutrality because the bio-fuel boiler uses waste vegetable oil as one of the fuels.The plasma-chemical hybrid NOx removal system has two processes:NO oxidation by ozone produced from plasma ozonizers and NO2 removal using a NazSO3 chemical scrubber.Test demonstrations of the system are carded out for mixed oils(mixture of A-heavy oil and waste vegetable oil).Stable combustion is achieved for the mixed oil(20-50%waste vegetable oil).