木炭の製造
たたら製鉄では、木炭は燃料と還元剤の両方の役割を果たす。木炭を燃やすと一酸化炭素が発生し、これが酸化鉄（砂鉄の最大成分）と反応して酸素を除去し、元素状鉄を生成する。
たたらの木炭は、ナラ、マツ、クリなどさまざまな木から作られた。
木は、火がつかないように低酸素の環境で数百度まで加熱して炭にした下の大きな木片のように高殿の炉の燃料として使われた木炭と、大鍛冶場(中)や家庭で使われた木炭(右)は、用途に応じて異なる方法で作られた。たたら炭は低温で長時間加熱されるため、揮発性有機物が多く残り、固定炭素の含有量が少なく、より早く、より熱く燃えた。
木炭用の木材を大量に輸送するにはコストがかかるため、製鉄所は森林に覆われた山の近くに立地することが多かった。30年周期で伐採される森林資源を持続的に管理することは、経営者の責任であった。たたら炉1基を1年間稼働させるのに必要な森林面積は約110ヘクタールで、1サイクルで3,300ヘクタールが伐採され、炭になったことになる。
Charcoal Production
In the tatara ironmaking process, charcoal acts as both a fuel and a reducing agent. The burning of charcoal produces carbon monoxide, which reacts with and removes the oxygen from iron oxide (the largest component of iron sand) to create elemental iron.
Charcoal for tatara ironmaking was made from many different types of wood, including oak, pine, and chestnut. The wood was made into charcoal by heating it to hundreds of degrees Celsius in a low-oxygen environment that prevented it from catching fire. The charcoal used to fuel the furnace in the takadono workshop, like the larger pieces displayed below, and the charcoal used in ōkajiba forges (middle) and households (right) were made using different methods for different purposes. Tatara charcoal was heated longer at a lower temperature, leaving more volatile organic matter and a lower fixed carbon content, which caused it to burn faster and hotter.
Given the cost of transporting large quantities of timber for charcoal, ironworks were often located near forested mountains where wood could easily be gathered. The proprietor was responsible for managing the forest resources sustainably by harvesting wood in 30-year cycles. Operating a single tatara furnace for one year required around 110 hectares of forest, meaning that 3,300 hectares were chopped down and turned to charcoal over the course of a single cycle.
