Carbon distribution and multi-criteria decision analysis of flexible waste biomass smouldering processing technologies.

Waste biomass treatment is a globally urgent matter which highly relates to environmental quality and human health. Here, a flexible suite of smouldering-based waste biomass processing technologies is developed and four processing strategies: (a) full smouldering, (b) partial smouldering, (c) full smouldering with a flame, and (d) partial smouldering with a flame, are proposed. The gaseous, liquid, and solid products of each strategy are quantified under various airflow rates. Then, a multi-criteria analysis in terms of environmental impact, carbon sequestration, waste removal efficiency, and by-product value is performed. The results show that full smouldering achieves the highest removal efficiency but generates significant greenhouse and toxic gases. Partial smouldering effectively generates stable biochar, sequesters over 30% carbon, and therefore reduces the greenhouse gases to the atmosphere. By applying a self-sustained flame, the toxic gases are significantly reduced to clean smouldering emissions. Finally, the process of partial smouldering with a flame is recommended to process the waste biomass that can sequester more carbon as biochar, minimize carbon emissions and mitigate the pollution. And the process of full smouldering with a flame is preferred to maximally reduce the waste volume with minimum environmental impact. This work enriches strategies for carbon sequestration and environmentally friendly waste biomass processing technologies.

Climate-induced Arctic-boreal peatland fire and carbon loss in the 21st century.

Boreal peatlands are increasingly vulnerable to wildfires as climate change continues accelerating. Fires consume substantial quantities of organic soils and rapidly transfer large stocks of terrestrial carbon to the atmosphere. Herein, we quantify the minimum environmental temperature from -45 °C to 45 °C that allows the moist peat to smolder, as the fire threshold of peatlands. We then apply a typical vertical soil temperature profile to estimate the future depth of burn and carbon emissions from boreal peatland fires under the impact of global warming. If the boreal region continues warming at a rate of 0.44 °C/decade, we estimate the carbon loss from the boreal peat fires on a warmer soil layer may increase from 143 Mt. in 2015 to 544 Mt. in 2100 and reach a total of 28 Gt in the 21st century. If the global human efforts successfully reduce the boreal warming rate to 0.3 °C/decade, the peat fire carbon loss would drop by 21% to 22 Gt in the 21st century. This work helps understand the vulnerability of boreal peatland to more frequent and severer wildfires driven by global warming and estimate climate-induced carbon emissions from boreal peatland fires in the 21st century.

An experimental method to investigate the water-based suppression of smoldering peat fire.

Smoldering wildfire in peatlands is one of the largest and most persistent fire phenomena on Earth, which contributes importantly to global carbon emissions. However, very few studies are available on how to extinguish these smoldering wildfires. Herein, we develop an experimental method to explore the effectiveness of the water-based suppression on smoldering peat fire, and the proposed method can also be used to simulate fire suppression by rain. The low-temperature drying process avoids the variation of hydrophobicity of peat soil. The validation shows that the proposed approach can provide a wide range of water-spray intensities with time variation, and two examples of successful suppression of smoldering peat fire and flaming wood crib fire were presented.•The design of small-scale combustion reactor for peat can mimic the smoldering peat fire in the field.•The effectiveness of water-based fire suppression technologies on peat fire are explored in the lab.•The proposed method can evaluate the effect of rain and weather on suppressing the smoldering wildfire.

Can rain suppress smoldering peat fire?

Smoldering wildfire in peatlands contributes significantly to global carbon emissions and regional haze events. Smoldering fire in peatlands is one of the largest and most persistent fire phenomena on Earth. Here we assess the underlying mechanism of rain in suppressing the smoldering peat fire in the shallow soil layer up to 15 cm deep through laboratory experiments. We show that the minimum rainfall intensity to extinguish the peat fire is roughly 4 mm/h, so that the persistent light rain cannot suppress such smoldering wildfire. The required rain duration, ∆t (min), for extinguishing smoldering peat fire decreases with the rainfall intensities, I (mm/h), as log10∆t = - 1.15log10I + 3.3, and is much longer than that for extinguishing flaming wildfire. We also identify that the required rainfall depth for extinguishing peat fire gradually decreases with the rainfall intensity and approaches a minimum value of 13 mm under violent rain. As rainfall intensity increases, the carbon emission flux from peat fire decreases. Therefore, we conclude that the short-term violent rain is most effective for suppressing the persistent smoldering peat fire. This research helps evaluate the impact of weather on the development of peat fire and improve the prediction of carbon emissions from peat fire with the use of regional weather models.