Renewable energy sources usually describe solar and wind power. Historically there have been low tech options, but today’s solutions tend to be high tech. Wood is renewable, but is smoky and low-tech so it must be bad. Right? Maybe not. Burning wood releases carbon dioxide, which is bad. Growing trees absorb carbon dioxide, which is good. As long as the local forests grow faster than our harvests, it is possible that using wood for energy is renewable and green – even if it is brown.