Another upcycled building material that is rising in popularity is ashcrete. It is concrete made from fly ash, which is a by-product of coal combustion. If we’re going to burn coal for fuels, despite its inefficiency and environmental impact, the least we can do is turn the nasty waste from it into something useful. Using fly ash is actually stronger, more durable, and more eco-friendly than traditional concrete. It even requires less water in the mix than concrete does. The downside is that coal needs to be burned to create it. Maybe one day, we will stop using coal for good and find better solutions. But for now, ashcrete is an awesome way to upcycle some waste products.