The $250 billion cement industry is one of the world’s most polluting: It accounts for 5 percent of man-made carbon-dioxide emissions each year. Yet for now, cement firms have not attracted the ire of environmental campaigners in the same way as oil firms and few are setting environmental targets that are tough enough.

The main reason is a lack so far of strong enough financial imperatives, but that is changing. And as is the case for many industries, going green could save the companies money. About one-third of cement’s production costs come from energy bills. For example, retrofitting old kilns used in making cement to improve thermal efficiency can lower the industry’s energy needs by two-fifths, according to the Carbon Disclosure Project, a research body.

About 4.3 billion tons of cement were consumed in 2014, with China alone needing more than half of that. China also produces 60 percent of the stuff, followed at a distance by India and the United States.

Finding ways to recycle materials or capture emissions to create new products could prove worthwhile. It could also reduce open-pit mining for limestone, which is especially destructive. Blue Planet, which creates building materials from waste from other cement makers, is providing materials for San Francisco’s new airport and has other projects across North America. Concrete is the “900-pound gorilla in the carbon footprint of any building,” says its CEO, Brent Constantz.

The group of cement bosses that environmentalists need to win round is small. Just six firms — LafargeHolcim, Anhui Conch, CNBM, Cemex, Heidelberg and Italcementi — dominate the global market. The last two are set to merge this year. Deals have multiplied as firms from the rich world have splurged on local firms in developing countries. Slowing growth in China has created a glut of cement in the country, which is likely to mean more deal-making.

Further consolidation, bringing economies of scale, ought to help the industry to clean up. China is to introduce a national carbon-trading policy in 2017, and the E.U.’s policies will reduce its emissions cap by 2.2 percent every year after 2020. The industry also is becoming more vulnerable to emissions-curbing legislation, says Phil Roseberg of Sanford C. Bernstein, a research firm.

Some cement giants are at last taking action. LafargeHolcim already uses an internal carbon price of $32 per ton; Heidelberg works with one of $23. In a changing regulatory and political environment, investors may start to see nasty cracks in the business model of any firm still stuck in the industry’s old, polluting ways.