Effect of carbonization temperature on fuel and caffeine adsorption characteristics of white pine and Norway spruce needle derived biochars

•White pine and norway spruce needles derived biochars were produced at 500, 700 & 900 ℃.•Calorific values of the biochars increased with carbonization temperature.•All the biochars were microporous in nature and had specific surface areas of 2–168 m2/g.•Biochars obtained at 900 ℃ attained caffeine adsorption capacities of 9.27–11.85 mg/g. The presence of pharmaceutical compounds in drinking water continues to be problematic in recent times. Adsorption of these compounds is an effective way to mitigate these problems to protect aquatic wildlife. Biochar is a renewable resource that can be used as an adsorption media in this role. This study explored the use of white pine (Pinus strobus) and Norway spruce (Picea abies) needles as feedstocks for producing biochars, which can be utilized as both an adsorbent and solid fuel. The effect of carbonization temperature (500, 700, & 900 ℃) on the solid fuel and caffeine adsorption characteristics of biochars derived from these feedstocks were investigated. The calorific values increased from 29.09–30.30 MJ/kg and 26.62–27.44 MJ/kg for white pine and Norway spruce needle derived biochars, respectively as the carbonization temperature increased. The ignition temperature increased from 390 to 480 ℃ for white pine needle derived biochars and from 368 to 400 °C for Norway spruce needle derived biochars as the carbonization temperature increased. The burnout temperatures for white pine needle derived biochars were between 670–775 ℃ while Norway spruce needle derived biochars presented burnout temperatures of 679–685 ℃. The specific surface areas of the biochars were between 1.72 and 167.71 m2/g. The monolayer caffeine adsorption capacities (qm) of the NS900 and WP900 biochars were 9.27 and 11.85 mg/g, respectively.