tylim/GettyThe Australian government has agreed to invest almost $53 million in a north Tasmanian company that will upgrade its coal-fired kiln to burn wood “waste” and used tyres for cement manufacturing.The Federal Minister for Climate Change, Chris Bowen, says this initiative will help decarbonise the Australian economy.However, the science is clear: burning forest biomass, or so-called forest “waste” – which could include dead trees, understorey vegetation and fallen logs – generates large amounts of carbon emissions. It will likely also accelerate poor forest health.The empirical evidence shows burning forest biomass to make concrete is poor climate policy, poor environmental and forest policy, and a poor use of taxpayer funds.Why is this happening?In line with climate change treaty commitments under the Paris Agreement, governments worldwide are working to decarbonise their economies in an attempt to limit global warming. This includes finding alternative sources of clean energy to using fossil fuel. This is especially important for carbon-intensive, high-polluting industries, such as concrete production. While about 56% of concrete emissions come from processing clinker (the base material for cement), 39% come from using fossil fuel to generate heat, and 14% from electricity. Unfortunately, forest biomass is increasingly being promoted as an energy source to replace fossil fuels, for example in the United Kingdom and Europe. Most forest biomass used to generate energy will likely be trees. And what is often referred to as “waste” is actually a critical part of the structure and composition of natural forests. For example, understorey vegetation and logs provide habitat for a wide range of animal species. They play an essential role in nutrient cycling, such as storing substantial amounts of carbon.Whilst forest biomass is technically a renewable resource, as trees can be regrown after logging, it is not a source of clean energy. This is because about half of tree biomass is carbon (assuming a moisture content of 45%). Therefore, burning a tonne of wood generates roughly a tonne of carbon dioxide emissions. Importantly, up to 30% of carbon dioxide emissions are still in the atmosphere after 1,000 years. Concrete and its primary ingredient, cement, account for up to 8% of global carbon emissions. This is because high heat is required to turn limestone into ‘clinker’. chameleonseye/Getty The time lag between release and absorptionCritically, there is a highly significant lag time, of decades to centuries, between carbon being instantaneously released from burning forest biomass and when it is removed from the atmosphere. These removals occur either by plant growth or through carbon making its way to the bottom of the ocean.The lag time between burning forest biomass and tree regrowth is important because the increase in atmospheric carbon dioxide concentrations causes even more climate change. This is one of the key reasons why widespread burning of forest biomass in some European countries threatens their ability to meet Paris Agreement greenhouse gas reduction targets.Furthermore, forest biomass has a far lower calorific content relative to coal. This means large quantities of forest material has to be burned to generate an equivalent amount of energy. This high demand for wood for biomass energy can contribute significantly to poor forest health. Notably, Australia, along with many other governments, has committed to ending deforestation and degradation by 2030. This recognises the importance of forest carbon sequestration and storage in meeting climate targets and achieving the Paris Agreement goals.Not an isolated exampleThe Tasmanian plan, that would see Cement Australia burn forest “waste” to generate energy, is far from an isolated case. There are well-developed plans for Verdant Earth Industries to reopen the former coal-fired Redbank Power Station in the Hunter Valley, in New South Wales, and generate energy by burning hundreds of thousands of tonnes of “wood waste” annually. Much of this “waste” will likely be trees from forest and woodland regrowth, which are fundamental to the integrity of those ecosystems. This regrowth also provides habitat for a vast array of species, including a range of threatened species. Biomass burning is frequently supported by native forest logging advocates because of structural issues in the industry. These issues include attempts to extract some financial return from an industry that is largely unprofitable. The native forest sector produces primarily low-value, high-volume commodities such as [woodchips and paper pulp], whereas plantation forest sector dominates high-value sawn wood products.Similarly, state government forestry agencies have been unable to get market certification for wood products such as woodchips and pulpwood from bodies such as the Forest Stewardship Council. This is partly because the areas logged to produce wood products are often are home to a diverse range of plants and animals that may be threatened by logging.Decarbonisation mattersWe fully acknowledge the efforts being made to explore how emissions-intensive industries can be decarbonised, such as reducing the clinker content in cement. However, Australian governments must stop using taxpayer money to subsidise projects that entail large-scale burning of forest and woodland biomass for industrial energy.Alternative forms of energy, including concentrated solar power, will be important in this regard. Unlike forest biomass burning, these are both renewable and clean sources of energy. A response was sought from Cement Australia.David Lindenmayer receives funding from the Australian government, the Victorian government and the Australian Research Council. He is a Councillor with the Biodiversity Council and a Fellow of the Australian Academy of Science, the National Academy of Science (USA), the American Association for the Advancement of Science, the Ecological Society of America, the Royal Society of Victoria, and the Royal Zoological Society of NSW. Brendan Mackey receives funding from the National Environment Science Programme, the Australian Research Council, and the Global Environment Facility. He has previously received funding from the Queensland, NSW and Tasmanian governments. He is a volunteer member of the Great Eastern Ranges Initiative board as a science adviser. He is a member of the Ecological Society of Australia, the Society for Conservation Biology and the Royal Meteorological Society.