Biomass pyrolysis is the thermal decomposition of biomass occurring in the absence of oxygen. It is the fundamental chemical reaction that is the precursor of both the combustion and gasification processes and occurs naturally in the first two seconds. The products of biomass pyrolysis include biochar, bio-oil and gases including methane, hydrogen, carbon monoxide, and carbon dioxide.
當有機物在惰性氣氛中加熱時，熱解過程包括同時和連續反應。在生物質中的有機成分在350℃〜550℃開始進行熱分解，并在無空氣/氧氣時上升到700℃〜800℃。生物質中碳、氫、氧的化合物長鏈分解成較小的分子，熱解條件下產生氣體、可冷凝液體（焦油和油）和固體炭。這些的分解速度和程度取決于反應器的溫度的工藝參數，生物質加熱速率、壓力、反應器結構以及原料等。The pyrolysis process consists of both simultaneous and successive reactions when organic material is heated in a non-reactive atmosphere. Thermal decomposition of organic components in biomass starts at 350 °C–550 °C and goes up to 700 °C–800 °C in the absence of air/oxygen. The long chains of carbon, hydrogen and oxygen compounds in biomass break down into smaller molecules in the form of gases, condensable vapours (tars and oils) and solid charcoal under pyrolysis conditions. Rate and extent of decomposition of each of these components depends on the process parameters of the reactor temperature, biomass heating rate, pressure, reactor configuration, feedstock etc熱解產物取決于熱環境和最終溫度，在小于450℃的低溫下，升溫速率很慢時，主要產生生物質炭，而在大于800℃高溫下，升溫速率很快時，主要產生氣體。在中間溫度和相對較高的升溫速率，主要產物為生物油。Depending on the thermal environment and the final temperature, pyrolysis will yield mainly biochar at low temperatures, less than 450 ℃, when the heating rate is quite slow, and mainly gases at high temperatures, greater than 800 ℃, with rapid heating rates. At an intermediate temperature and under relatively high heating rates, the main product is bio-oil.The essential features of a fast pyrolysis process are:Very high heating and heat transfer rates, which require a finely ground feed.Carefully controlled reaction temperature of around 500℃ in the vapour phase.Residence time of pyrolysis vapours in the reactor less than 1 secQuenching (rapid cooling) of the pyrolysis vapours to give the bio-oil product.熱解可以在相對小規模和較遠的地方進行，提高生物質資源的能量密度、降低運輸和處理成本。傳熱是熱解過程中的一個關鍵環節，吸熱和充分傳熱必須滿足過程的熱需求。生物質熱解為有機物轉換成能源產品提供提供了一種靈活引人注目的方式，可用于生產熱、點、化工產品等。
Pyrolysis can be performed at relatively small scale and at remote locations which enhance energy density of the biomass resource and reduce transport and handling costs. Heat transfer is a critical area in pyrolysis as the pyrolysis process is endothermic and sufficient heat transfer surface has to be provided to meet process heat needs. Biomass pyrolysis offers a flexible and attractive way of converting organic matter into energy products which can be successfully used for the production of heat, power and chemicals.廣泛的生物質原料可用于熱解過程中。熱解過程非常注重原料的含水量，即10％左右水分含量。更高的水分含量的話，會產生高水量，在更低水分含量的話，會有只產生粉塵而不是油的風險。高水分的廢物流，如污泥和肉類加工廢料，需要在熱解反應之前進行干燥。
A wide range of biomass feedstocks can be used in pyrolysis processes. The pyrolysis process is very dependent on the moisture content of the feedstock, which should be around 10%. At higher moisture contents, high levels of water are produced and at lower levels there is a risk that the process only produces dust instead of oil. High-moisture waste streams, such as sludge and meat processing wastes, require drying before subjecting to pyrolysis.