There are two types of redwood native to the US and people often get them confused. There are the coast redwoods that grow along the north coast of California and a small area of SW Oregon. These are the tallest trees in the world. Then there are the sequoia redwoods that grow high in the Sierra Nevada mountains. These don’t grow as tall as the coast redwoods, but they make for it in bulk from their massive diameters. These are the largest trees in the world, exceeding the taller coast redwoods in volume.
Coast redwood firewood is a soft low density wood with low BTU. It makes great kindling because it splits easily and is usually straight grained. It can crackle when it burns so it can be nice for a fireplace, but it burns up quickly. In areas where redwood is abundant, a lot of people avoid redwood in favour of hardwoods and Douglas fir, which are longer lasting. But if the price is right, or free, redwood firewood is worth burning. It is good for starting fires or when you only need a short burn.
If you have redwood logs of any size, it may be worth more for lumber or the many other uses for redwood than it would be as firewood.
Coast redwoods grow very fast and are one of the few conifers that will sprout back from the stump after you cut them down. These sprouts grow very quickly into new trees, and it also grows quickly from redwood seedlings. Although there are is a limited amount of the huge old growth redwood forests left, redwood in general are not endangered as some might lead you to believe. Anyone who has ever dealt with redwood forests knows how hardy they are and how vigorously they grow.
It is hard to find any information about sequoia redwood firewood. I have heard that it burns similar to incense cedar. It is a low density softwood so it would burn fast, but I have heard it burns with nice glowing coals.
If you have experience with wither coast or sequoia redwood, please post below.