Few fields are changing as quickly as climate tech. In the last five years, it’s undergone a radical transformation, blossoming from a niche area to a broad sector full of promising niches. With that diversification comes risk and opportunity.

And choices. So, so many choices. With the world looking to revamp nearly every corner of the global economy, there is a seemingly unending supply of startups in which to invest. There’s no way to create a definitive list, but here are three areas that deserve a closer look.

Enhanced rock weathering

With humans on track to blow through the “safe” amount of global warming in less than five years, carbon removal has been getting a lot of attention. There are lots of ways to do it, too: from big carbon filters and enhanced algae to rocks. Yes, rocks.

Several types of rocks naturally draw carbon dioxide from the atmosphere and transform it into a stable mineral. Problem is, that process is happening too slowly to have any effect on the colossal amounts of carbon we’ve pumped into the atmosphere.

One of the easiest ways to speed that process up is to expose more rock to the atmosphere by crushing it to bits and spreading it out over a wide area. That may not sound very appealing, but it is to farmers.

Farmers already spend lots of money on soil amendments, which includes everything from synthetic fertilizers to compost and manure. In certain regions with acidic soils, farmers also apply crushed limestone to raise the pH in the area.