In recent years, biochar has attracted considerable attention due to its unique characteristics and wide applications in agricultural and environmental areas. Biochar is recognized for its potential role in carbon sequestration, reduction of greenhouse gas emissions, soil amendment, bioenergy production and waste mitigation. The current review discusses on the utilization of various lignocellulosic and lignin-based feedstocks for the biochar production. However, the quality of biochar varies among different thermo-conversion technologies due to the differences in their key process parameters and the feedstock composition. This article aims to review two production technologies for lignocellulosic and lignin-based biochar, namely, slow pyrolysis and fast pyrolysis. The effects of feedstock composition (cellulose, hemicellulose, lignin) and pyrolysis conditions such as temperature and heating rate on the quality of biochar are compared. The relationship between the feedstocks composition, temperature, heating rate of pyrolysis and the quality of biochar are also discussed. Future work would further correlate the effects of feedstock composition and process parameters on the quality of biochar such as surface area and functionality.

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Graphical abstract In this study, a systematic procedure for establishing the relationship between particulate matter (PM) and microbial counts in four operating rooms (ORs) was developed. The ORs are located in a private hospital on the western coast of Peninsular Malaysia. The objective of developing the systematic procedure is to ensure that the correlation between the PMs and microbial counts are valid. Each of the procedures is conducted based on the ISO, IEST, and NEBB standards. The procedures involved verifying the operating parameters are air change rate, room differential pressure, relative humidity, and air temperature. Upon verifying that the OR parameters are in the recommended operating range, the measurements of the PMs and sampling of the microbes were conducted. The TSI 9510-02 particle counter was used to measure three different sizes of PMs: PM 0.5, PM 5, and PM 10. The MAS-100ECO air sampler was used to quantify the microbial counts. The present study confirms that PM 0.5 does not have an apparent positive correlation with the microbial count. However, the evident correlation of 7% and 15% were identified for both PM 5 and PM 10, respectively. Therefore, it is suggested that frequent monitoring of both PM 5 and PM 10 should be practised in an OR before each surgical procedure. This correlation approach could provide an instantaneous estimation of the microbial counts present in the OR.