Large scale biomass systems require a fairly large amount of space, but they can be housed outside or in a building, provided there is a sufficient access for fuel as most large scale units have hoppers, with fully automated fueling systems, that draw the biomass from large stores nearby. Although biomass systems and the processes they use produce and release some CO2 into the atmosphere when combusted, it is no more than the amount absorbed by the plants during their lifetime (with the exception of fuel transportation). Biomass fuel is therefore regarded as being a low carbon technology, especially if the biomass fuel used is from sustainable and local sources. The way Commercial biomass boilers burn fuel and the biomass fuel they use make them as convenient to use and have installed as fossil fuel boilers are.