Bricks used in construction have a huge climate footprint. Engineers in Uganda are seeking to change that. It’s an urgent task in a country with a booming population and construction industry.
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00:00 These bricks are dry-pressed and not fired in a kiln.
00:05 They are made of sand and a bit of cement and a lot of muscle power.
00:10 And no wood since there is no kiln.
00:12 Ugandan architect Stephen Juko believes a switch to alternative construction materials
00:18 is long overdue.
00:20 When you drive through many forests, they are no longer forests, you don't feel that
00:24 darkness surrounding you.
00:26 So the problem is dire that we need to stop firing bricks to make our houses.
00:33 About a quarter of each brick is made out of cement though, and cement manufacturing
00:38 produces a lot of CO2.
00:40 But the interlocking bricks are easy to assemble, so they need less cement than regular ones
00:46 do.
00:49 The block that comes out is the interlocking.
00:52 Interlocks at the top, at the sides and the bottom.
00:55 So by that way as well we reduce the amount of cement used to build a structure.
01:00 In that way we are reducing the emissions by reducing the cement and the amount of trees
01:07 that or vegetation that would have been cut down to, in order to produce a brick or to
01:14 build a house.
01:16 In Uganda, most houses are still made out of kiln-fired bricks, which mostly use firewood.
01:23 There are thousands of small brick-making businesses like this throughout the country.
01:29 And the ongoing housing shortage means their bricks are in high demand.
01:34 Using pressed bricks instead could help save a lot of firewood.
01:38 The homes still look the same, and for the homeowners, they also offer other benefits.
01:45 Constructing with interlocking bricks enabled us to have our building in less than two months.
01:54 It fit in our budget and then we also saved because the money that we would have used
02:02 to transport materials.
02:06 The construction industry is a major climate killer.
02:10 Cement manufacturing accounts for some 8% of global carbon emissions.
02:18 That's why engineers are studying ways to reduce or eliminate cement in brick-making,
02:23 including Marion Nwahereza.
02:26 She works for Eco-Concrete, a company that makes cement using of volcanic ash.
02:32 Traditional cement is made out of limestone and firing it emits massive amounts of CO2.
02:38 When you heat one kilogram of limestone, you emit about 44% of it as carbon dioxide.
02:47 You only retain 55.
02:49 So for one ton, when you put in all other production emissions, you find that for one
02:54 ton, you're emitting about 500 kilograms of carbon dioxide.
02:58 That is about half of it.
03:01 The engineer has been working with students at Makarera University in Kampala on the new
03:06 process.
03:07 Volcanic ash is plentiful in Uganda.
03:10 Just like in ordinary cement, the recipe calls for sodium hydroxide.
03:14 But the mixture doesn't need to be heated, so the process uses five times less energy
03:19 than limestone-based cement.
03:22 The result is what's called geopolymer cement.
03:25 Their tests have shown that this product could cut emissions by 80% compared to Portland
03:31 cement, which is used around the world.
03:36 We've been using it in blocks, building blocks.
03:39 And we've also done water absorption tests, and these materials are proven to be better
03:44 than Portland cement.
03:46 The engineer and the architect share a common goal - to help make Uganda's construction
03:51 industry more sustainable.
03:55 The majority of people can do our work, what they eat, how they get to work.
03:59 But with engineers it's different.
04:00 They actually have the space to innovate and reduce carbon dioxide emissions.
04:07 As someone who studied in the building profession, architecture, and then with my colleagues
04:13 in engineering, we're responsible for many of the designs.
04:17 So the process starts with us.
04:19 The recommendations we make, or the specifications we give to our clients.
04:25 While Stephen Juko has been using his bricks for several years, Marion Nwa-Hereza is starting
04:31 pilot production, and hopes she'll soon get the green light from local authorities.