Effects Of Feedstock Type, Production Method, Pyrolysis Temperature On Biochar And Hydrochar Properties And Their Effects On Seed Germination

Biochar is a pyrogenic black carbon derived from thermal conversion of biomass feedstocks, including agricultural and forest residuals, in an inert atmosphere. The functions and applications of biochars may vary because of their different physicochemical properties. In order to promote the biochar technology to benefit the environment and society, it is thus critical to understand the key production factors that control the physicochemical properties of biochars.This work explored the effect of temperature, production method, and feedstock type on the physicochemical and biological properties of biochars and hydrochars. Biochars and hydrochars made at lower temperatures had higher production rates. Higher pyrolysis temperatures could not only increase carbon content of biochars but also produce higher thermal stability biochars, which only started to decompose in air after400～450℃. The production method showed strong effect on biochar properties. Compared to the dry-pyrolysis biochars derived from the same feedstocks, the hydrochars had more acidic pH values and lower carbon contents. The results showed that feedstock types can also influence characteristics of the biochars. All of the chars showed no statistically significant effects on plant seed germination and seedling growth and thus could be used as soil amendment. Our findings indicated that biochars with different properties could be developed by changing production conditions to better satisfy their environmental applications.Sorption of lead on the chitosan-modified biochar greatly reduced its metal toxicity and bioavailability. Both seed germination rate and seedling growth of the Pb-laden BB-C were similar to that of control groups without lead. In addition, uptake of lead by plants was reduced about60%when lead was sorbed onto the chitosan-modified biochar. This work suggests that chitosan-modified biochars may be used as an effective, low-cost, and environmental-friendly adsorbent to remediate heavy metal contamination in the environment.