canada announced plans to phase-out coal-fired electricity generation by 2030. therefore, in 2014, the province of ontario has phased out the use of coal in the production of electricity. former coal powered generating stations have been converted to use biomass. ontario power generation, ontario’s largest producer of electricity, has converted former coal powered thunder bay generating station (tbgs) to use advanced wood pellets (awp), which are produced from thermally treated biomass. the thermal treatment with steam explosion makes the awp more durable and water resistant as compared to conventional wood pellets, hence allowing tbgs to use the same handling and storage equipment they used for coal, including outside storage of awp. however, the quality properties of awp may degrade due to exposure to weather conditions while stored outside, affecting their performance as a fuel. the purpose of this study was to analyze the degradation of awp while stored outside, and to give recommendations for the most effective storage approach to the industry. we examined the trends and level of degradation of awp quality properties, while stored outside in uncovered and covered piles, through a period of 11 months. additionally, we monitored internal temperature trends of the piles, to assess if there is any risk of self-heating, and tested fresh factory samples, which served as a baseline. the results showed that awp moisture content is highly influenced by weather conditions (in the first place precipitation), with moisture content directly or indirectly affecting the rest of the properties. furthermore, the covered pile displayed significantly better preservation of properties, while self-heating was not observed in any of the piles. we recommend covering awp piles, especially in the winter months, to reduce snow pack that could thaw and penetrate into the pile in the spring. this study also contributes to the existing knowledge in the biomass area, since there are very few studies done on awp storage and quality properties.