No one is going to argue the manufacturing of cement doesn’t come at a price: it burns energy and emits greenhouse gases.
The construction industry itself has been working hard to find solutions, from sourcing waste materials to burn in the kilns and capturing and cleaning the effluent smoke. Still, looming carbon taxes — whether direct or in the form of Cap and Trade — are going to pose problems for the cement industry, say experts.
The concept of a burn-free cement, created with almost zero energy and zero emissions, is becoming more intriguing. There have been research papers over the last decade or so which re-examined theories around how cement can be created using microbials and how much sand can be displaced in the process of making concrete by using silica rich plant material such as rice husks and corn cobs.
Dr. Mahsa Madani Hosseini researched silica rich plants during her PhD in Environmental Engineering at Montreal’s Concordia University. Hosseini and her colleagues published a paper looking at the viability of replacing or at least displacing sand in cement production.
"What we called biocement in our paper is a blend of bio-silica, produced from combustion of organic residues, with Portland cement," he said. "The biosilica could come from agricultural wastes such as corn cob, wheat straw, rice husk…or industrial wastes such as saw dust, wood chips, and sewage sludge."
She said many researchers have shown a blend of biosilica with Portland cement increases the compressive strength of concrete and also increases resistance to acid attack, she said.
"I believe that these research results motivated the cement industry to produce biocement. For example there’s a Colorado cement plant in the U.S. which has produced cement using rice husk, saw dust, wood chips."
It’s hard to find high silica producing plants in Canada since most are in the tropics and of course our climate is different here, Hosseini said.
"We did find that corn cobs were high in silica. You can burn them in the kiln with the limestone as energy to make the cement and then the ashes can be incorporated as silica. My co-authors are now working with switchgrass and getting positive findings. It’s possible but it’s still very much in theory. We’re a long way from using plant silica to make cement commercially."
Looking at the challenge from a different perspective and closer to production is bioMason, a U.S. start-up founded by architect Ginger Krieg Dosier in 2012 which aims to make concrete bricks using bacteria and attain zero emissions.
The concept is simple. They mix bacteria in with sand and other materials and over a period of days, under the right condition, the micro-organisms go to work, creating calcium carbonate and with the mix in a mould, making concrete blocks suitable for construction jobs.
It’s not as off the wall as it sounds because it’s drawn from nature. Biocement emerged from a study of coral structure: a hard cementitious material created by nature in ambient sea temperatures with low energy and material inputs.
The process has since been refined and continually optimized to increase performance and reduce production costs. BioMason has moved from a research and development lab at North Carolina’s Triangle Research Park to a larger development facility where they are working to make the process commercially viable.
BioMason notes an estimated 1.23 trillion bricks are manufactured every year, pushing out 800 million tons of carbon emissions, mostly from the fossil fuels in the firing process. In its pitch to investors, bioMason figures brick manufacturing accounts for approximately eight per cent of all global carbon emissions.
Dosier, president and CEO of bioMason, thinks microbials are a better solution and envisions her process being used at on site location to create concrete blocks. So far bioMason has snared some $5 million in investments and expects to launch commercially next year.
Other companies are also working to produce biocement, such as BioCement Technologies in Seattle, which is developing patented, microbial soil engineering solutions to improve soil quality in unpaved roads and surfaces, collapsible soils, controlling the hydraulic conductivity of soils, combating soil liquefaction, and remediating heavy metal contamination in soils.
Founder Dr. Malcolm Burbank identified a class of bacteria indigenous to almost all soils which can hydrolyze urea in the presence of calcium chloride to precipitate calcium carbonate.
This reduces permeability and compressibility of soil while significantly increasing soil strength.
Recent Comments
comments for this post are closed