Cremation is an increasingly popular method for the disposal of human remains due to its relatively low cost and presumed low environmental impact compared to traditional burial. Both the fumes expelled during cremation and the mineralized remains of the skeleton (called “cremains”) are possible sources of toxic waste. Though the fumes are filtered for particles and certain compounds, crematoriums still spew toxins such as carbon dioxide and mercury into the atmosphere. Cremains are often powdered and sprinkled somewhere in memorial, releasing whatever compounds and toxins found in them back into the environment in a form that is easily picked up by wind or water.
Overall, even with the use of fossil fuels as a heat source, cremation contributes very little to atmospheric, water or soil pollution by metals such as mercury, lead or cadmium; or by green house gases such as carbon dioxide.
It is with no doubt that cremation saves a lot of land space because it does not require a large area below the ground to be buried, thus does not utilized much of the Earth’s surface. Unlike caskets that specifically need to be buried in cemeteries or mausoleums, urns can be easily placed in a small spaces often times even in their own homes, or ashes can be scattered in a cremation garden or memorial parks.
(Source cremation association of North America)