Biochar is not a complete cooling method, but it is an important component of cooling via CO2 removal. CO2, unlike methane, cannot be “destroyed”. If and when it has been removed from the air, e.g. by DAC, it must be stored safely to the ground. This process is called “sequestration”. Biochar is one possible sequestration method. It is natural and safe.
Quote from biochar-us (Link 1)
Biochar Slows Climate Change
The Carbon Cycle— The movement of carbon, in its many forms, between the biosphere, atmosphere, oceans and Earth’s crust is called the carbon cycle. Plants absorb carbon dioxide (CO2) from the atmosphere during photosynthesis and release oxygen (O2) during respiration. Animals breathe in O2 and breathe out CO2. All organisms release carbon and CO2 during decomposition or burning. This active carbon cycle, with CO2 being released into the atmosphere and reabsorbed by plants and oceans, has been balanced for millennia.
So What’s Causing the Climate to Change?— Simply, Earth’s atmospheric CO2 is out of balance. Scientists know that Earth’s climate has changed cyclically over millions of years. However, never in geologic history has it changed so dramatically, so fast. The spike in global warming —and atmospheric CO2— coincides with the Industrial Revolution when fossil fuels began to be widely used. Fossil fuels originated from plants and animals. Just like plants today, this ancient biomass contains a lot of carbon but it’s been sequestered in the ground in the inactive carbon cycle.
Image source: Link 1 Endquote