- 9 hours ago
From sandy islands to polluted cities, one scientist is giving land a second chance, proving degraded soil can recover. Plus: How recycled coal can purify rivers and revolutionize wastewater treatment.
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00:07This year, I promised myself three things.
00:10Be more intentional with the people I meet, less screen time, and fewer excuses.
00:16So far, I'm doing very well on the excuses.
00:19But for the screen time, let's just see, I need a second chance.
01:01Collecting seaweed for the garden.
01:09Caroline Kennedy runs a camp on a small island off Kiwaiu, off the Kenyan coast.
01:15She'll use the seaweed to help improve her vegetable beds.
01:19So we actually don't have soil here. It's sand.
01:23So the challenge is trying to make soil and source water.
01:30And use it as economically as possible because we don't have running water here.
01:36All our water is brought in by donkeys.
01:39And that's why I contacted Sue so that she could help us understand how to do things properly.
01:48Biologist Sukahumbu specializes in regenerating soil.
01:53She's become known as Kenya's soil whisperer.
01:56But this is the first time she's attempted to transform sand into fertile soil under such difficult conditions.
02:08I absolutely do believe that we can turn this sand into soil that will produce food for consumption here.
02:16We do have to look at other issues.
02:18The heat, the humidity, the moisture that's lost in the ground very, very quickly.
02:29We also have to look at the salinity of the soil and also the salinity of the air.
02:36But if we look around us, everything is green.
02:41Nobody's been putting fertilizers on this place.
02:44But how could vegetables possibly grow and thrive in these conditions?
02:50Sue Kuhumbu's approach, inoculating the ground, which means adding microorganisms.
02:56Kitchen scraps like fruit peelings or leaves are perfectly sufficient to provide the nutrients needed.
03:02Microbes then begin to form in the soil.
03:06Sukahumbu adopted this concept from American microbiologist Elaine Inham, who passed away recently.
03:13Going through her course and seeing that happen and learning how to make compost as a biological inoculant, not as
03:22a fertilizer.
03:23And then seeing it work, seeing it change, seeing plants react differently, seeing entire ecosystems change based on igniting the
03:34life underground as opposed to continuing killing the life underground and pushing in a chemical support system.
03:41It's just, yeah, it's, it's, it's, it's, it's, for me, it has been the most eye-opening journey in all,
03:49in my entire journey in agriculture.
03:51Now, she can attest whether this works with sand as well.
03:55The most important thing is to keep the ground moist.
03:58To do this, the team uses leaves from native plants like aloe vera or the algae they collected in the
04:05morning.
04:05They also measure moisture levels in the ground at regular intervals.
04:10This helps them save a lot of water.
04:13At first, they were using 200 liters a day.
04:17Now, they only water when the plants need it.
04:20And, equally important, checking whether enough minerals are present in the ground.
04:27Whether it's sand or soil, the scientist wants to bring out the best in every type of ground.
04:34For more than 20 years, Sukahumbu has been working to improve soil quality in Kenya.
04:41Over 60% of the farmland in Kenya has degraded soil.
04:45Across Africa, generally, that figure is at least 65%.
04:49In major cities like the capital, Nairobi, the soil is also heavily contaminated,
04:56mainly due to pollution from traffic and discarded waste.
04:59Soil degradation in urban settlements is a really, really big issue,
05:03and especially around informal settlements, because there's a lot of toxicity that's in the soil.
05:08There's a lot of compaction that's in the soil, as you can see from this area.
05:13When you grow plants in a toxic environment, A, it's more difficult to grow,
05:17but those plants also can suck up those toxins.
05:21Christopher Waidhaka has been experimenting with ways to improve the soil in the city
05:26with his community-based organization, Comgreens Solutions.
05:31Three years ago, he took an online course led by Sukahumbu.
05:35Now, they are meeting in person for the first time in the neighborhood of Korogosho,
05:41where Christopher lives.
05:42It's not far from one of the capital's largest landfills.
05:46And I find that we are close to the dump site, which is like a kilometer.
05:50I find that this area is polluted, even the soil, not only the air,
05:54even the soil is polluted, the water is polluted.
05:56And you can believe if the water is polluted, the soil is also polluted.
06:01In 2017, he and other residents launched the Comgreen Initiative to improve their neighborhood.
06:07Their first project was to clean up the banks of the Nairobi River and create a park.
06:13Later, they also began revitalizing the soil on their own property and growing vegetables.
06:20The soil which we are having here, through the training, we know how to make the soil to look healthy.
06:27And apart of that, also, we are using compost, which is organic.
06:30Back on Kiwayu Island, they are also early signs of success.
06:35Some trees have taken root, and one variety of beans is doing well.
06:41Zukahumbu is hopeful.
06:42Tests in her mobile lab show that microbes have accumulated in the sandy soil.
06:47That means that humans can form, providing essential nutrients.
06:52I think that there's huge potential to restore soils anywhere.
06:56The microbial story is what needs to be corrected, and microbes have amazing remediation capacities.
07:07It looks like her experiment here will be a success, allowing organic vegetables to thrive in the sand, despite the
07:16adverse conditions.
07:19What struck me the most in this story is just how invisible soil is to most of us, and yet
07:25how deeply it shapes everything, from the food we eat to the health and potential of a nation.
07:31I've learned that restoring soil isn't just about farming.
07:34It's about rebuilding life from the ground up and rethinking how we grow, how we feed and sustain our cities
07:41and our future.
07:50In Dakar, Senecal's rapidly growing capital, green space is becoming harder to find.
07:57And there's little room left for traditional vegetable gardens.
08:01But there is unused space right above people's heads, on rooftops and terraces across the city.
08:08When Maimouna Cham looked at her own terrace, she saw an opportunity.
08:12She's a trained engineer and interior designer.
08:18I asked myself, what could be more beautiful than flowers?
08:21I started with just one plant, and then it became an addiction.
08:25Little by little, my terrace filled up.
08:29What began with a single plant is now a thriving terrace garden.
08:33Today, she grows herbs like thyme and oregano,
08:37along with pigeon peas, tomatoes, and other vegetables.
08:47I especially like cherry tomatoes, nana mint, lemongrass, and lots of aromatic herbs.
08:53That's what I use every day in my cooking.
08:55I'm a big fan of cherry tomatoes, so of course I grow them in my garden.
09:00Carmel Market, in the heart of Dakar, is one of the city's most popular markets.
09:04But fresh vegetables are increasingly expensive.
09:09Many shoppers are buying only what they absolutely need.
09:16Sometimes I buy smaller quantities.
09:19Instead of a kilo, I'll buy only 500 grams.
09:25I need some kinds of vegetables to stay healthy.
09:33My Imuna isn't alone.
09:36Rooftop gardening is gaining ground.
09:39Programs run by the city of Dakar
09:41and the UN Food and Agricultural Organization
09:44have already trained more than 10,000 residents
09:47in micro-gardening techniques.
09:51Today, she shares gardening tips on social media,
09:54like how to prepare a fresh, tasty salad from her harvest.
10:01The garden has changed more than what's on her plate.
10:05It's made the terrace more welcoming.
10:10It helps our air quality.
10:13Dakar is a very dusty city.
10:14The plants give off oxygen, and we need that.
10:21With their gardens, people like Myimuna Chiam
10:24are bringing more green to Dakar,
10:26one rooftop at a time.
10:33Carbon has a dirty reputation, and for good reason.
10:38When coal is burned, it releases carbon dioxide
10:42and air pollutants, which are a big factor
10:45in driving climate change.
10:47But if you process carbon differently,
10:50it can become a powerful filter.
10:52Not this piece exactly, but a special extraporous version.
10:59In Germany, it has given one river a second chance.
11:03This was once Europe's dirtiest river.
11:06It flowed right through the Ruhr region,
11:09which was Germany's main coal mining area for decades.
11:12Toxic wastewater from mining and industry
11:15all ended up in the river Emscher.
11:17As did residents' untreated sewage.
11:19They called the river the Krap Basin.
11:22Now that industry has gone.
11:24The coal mines are museums.
11:26And the Emscher is now one of the cleanest rivers in Germany.
11:31So what happened?
11:33Today, the entire sewage system runs underground,
11:37invisible and odorless.
11:39Scientists, too, are impressed by the river's transformation.
11:46Until quite recently, the Emscher really was an open sewage canal.
11:51It's only been just over four years
11:53since the river became wastewater-free, as we say.
11:56That means it's free of untreated sewage.
12:00Nadine Gerner has been monitoring the Emscher for years.
12:04More than half of the roughly 350-kilometer-long river
12:07has already been renaturalized.
12:09The Emscher flows through a heavily urbanized area,
12:13home to millions of people.
12:15It empties into the Rhine River,
12:16near the town of Dinslaken.
12:21In the early 20th century,
12:23large parts of the river were straightened for industrial use.
12:27This was reversed in recent decades.
12:29The river is finding its natural course again.
12:33And water quality has improved.
12:37Yes, water quality has been developing quite well since then.
12:40But we still have some way to go.
12:42And we're already much closer to having a clean river again.
12:47Thanks in part to modern engineering,
12:50the nearby Deutmunt-Deusen wastewater treatment plant
12:53is leading the way in Europe
12:55with technology that will be mandatory in the EU from 2045.
12:59It costs over 45 million euros, but can do a lot.
13:04A typical wastewater treatment process normally consists of three stages.
13:09Mechanical, biological and chemical treatment.
13:12After that, we've removed all solid substances from the wastewater
13:16and dissolved nutrients like carbon, nitrogen and phosphorus.
13:20But there are still other dissolved substances in the water
13:24that we can't remove with these processes.
13:26For example, pharmaceutical residues.
13:29Those can be removed with the fourth treatment stage.
13:34Now for the first time, residues of medicines, pesticides,
13:38crop protection products, corrosion inhibitors
13:40and synthetic fragrances are all filtered out.
13:44The process involves these blue mats,
13:47expensive, high-tech components,
13:49which form the world's largest cloth filter system.
13:52In this process, the water is purified
13:55with the help of activated carbon.
13:58Yes, that black carbon.
14:00We add the activated carbon to the water and mix it in.
14:04The trace substances we talked about,
14:06those that aren't removed in the three conventional stages,
14:10bind to the activated carbon.
14:12These are microscopically small particles
14:15with a huge surface area.
14:17The contaminants adhere to the activated carbon
14:20and are thus removed from the water phase.
14:25But what is activated carbon?
14:28It's a form of carbon that has a high internal surface area
14:31and is a powerful binding agent.
14:34Usually it's made from natural resources
14:36like wood, coconut shells or coal.
14:38A company near Bonn in western Germany
14:41even recycles activated carbon.
14:43The firm was founded by Wolfgang Esser-Schnittmann
14:47and is now led by his daughter.
14:51To produce one ton of activated carbon,
14:54you need around 15 tons of fossil or carbon-containing raw material.
14:58If you recover that ton of activated carbon through recycling,
15:02the carbon footprint is drastically reduced.
15:05In our process, we're at around 0.2 tons of CO2 per ton of activated carbon,
15:11a reduction of well over 90 percent.
15:19In a thermal process, the activated carbon is heated.
15:24This creates a sponge-like surface that can absorb pollutants.
15:30The procedure can be repeated as often as needed.
15:37The company has developed a circular system
15:40to recycle activated carbon from wastewater or from industrial plants.
15:47For example, we take back wastewater from individual treatment plants,
15:52analyze it in our laboratory,
15:54and then develop activated carbon tailored specifically to that site,
15:58making it especially efficient and economical.
16:03Back to the Emsher.
16:05Thanks in part to water purification using activated carbon,
16:09the river has become much cleaner.
16:14We definitely have a variety of different species here,
16:18mainly freshwater crayfish, but also mayflies, at least two species.
16:23These are clear indicators of good water quality.
16:31Over 500 species have now returned to the river,
16:35including sticklebacks, trout, and the banded demoiselle.
16:38Thanks in part to the new treatment process at the wastewater plant
16:43and to activated carbon,
16:45the black gold that ultimately leads to clean water.
17:18馬ly tastes experienced,
17:18the invertebrate carbon already consume muchipper half.
17:18Tell me about this question in all the properties.
17:18I still think we have multarianism demanded before moving out.
17:18I am the person they wore saltly with an apple in the river.
17:18And what I believe is,
17:23Ghanian-born Ibrahim Mahama is one of the world's most influential artists.
17:28He is changing the way we think about art.
17:31He works globally, like at the Venice Biennale, where a gallery is exhibiting his new works.
17:36His pieces highlight social ills and global injustice, earning him international fame.
17:43For me, it's rather an opportunity to see that the work that we do, it means something
17:49to the world and to the communities that we come from.
17:52Because for us, the idea of making art has always been about the question of the gifts.
17:57What does art mean?
17:58And what are the associated responsibilities that come along with it?
18:01So when you're an artist, it's not just about making beautiful objects, but it's about the
18:04criticality that you also bring to the world.
18:07Mahama's work is far from glamorous.
18:09His international breakthrough came with art works comprising whole buildings draped
18:14with old jute sacks.
18:18The theatre in Ghana's capital city of Accra.
18:22The watchtower at the 2017 Castle Documenta.
18:28And this room at the 2015 Venice Biennale.
18:33The jute sacks were a statement.
18:35They symbolized the history of Ghana's cocoa trade.
18:38The cocoa beans leave the country and only the sack remains.
18:43I'm really interested in what happens to the bag once it is no longer be used for cocoa.
18:47The market women will use it to bag rice, maize, millet.
18:51At that point, it has really absorbed what all the politics in the history of the world
18:55within it in terms of like this kind of inter-global trade dialogues and all that.
19:00And also the inequalities that are absorbed within it in terms of like labor extraction and all kinds of other
19:05things.
19:05These used objects all have a history, telling stories of trade, labor and power.
19:11Their history continues to resonate.
19:14He even turns scrapped trains into art, like here at a Vienna exhibition in 2025.
19:20All the materials that I collect are normally things that you wouldn't look at twice.
19:24When you see them, you think, oh, these are old, they are discarded, they are dead.
19:29But it's the role of the artist in order to be able to have a vision and courage,
19:32in order to be able to, what, excavate and reawaken the senses within these materials.
19:39Several hundred people work at Ibrahim Mahama's red clay studio.
19:43They collect objects and process them into materials for artworks.
19:48Mahama could just as easily have a studio in an art capital like London or Paris,
19:53but he has deliberately chosen instead to invest in local infrastructure.
19:59The idea that we are producing it here, even repatriating that capital here,
20:04means that it's also keeping a history of craftsmanship alive.
20:07We are paying people.
20:09So aside, sometimes the work of art is not just necessarily the object that is produced,
20:13but it's also what the contribution, the capital that comes into the art,
20:19also makes to the local community, and for me that is very important.
20:23Besides the red clay studio, Ibrahim Mahama also founded the Savannah Centre for Contemporary Art in Tamale,
20:30an exhibition and workshop space.
20:37Culture is what drives the engine of the world, in terms of the soul of the world itself.
20:42So, whatever be the case, we need to be able to invest more in it,
20:46so that at least it can somehow give birth to a generation in the future
20:50that can somehow think about different ways of resolving the politics within the world.
20:55Can art change the world?
20:57Ibrahim Mahama is convinced it can.
21:29Ibrahim Mahama is what drives the world.
21:29it's more important than everyone else.
21:29It's really important to me to tell you.
21:29So, I think it is,
22:02Plastic waste and debris below its tranquil scenic surface, Lake Malawi looks very different.
22:12Since 2023, local divers in Cape McLear, led by Felix Sinossi, have been clearing plastic waste from the lakebed three
22:19times a week.
22:25The garbage underwater seems harmless, but it is destructive.
22:31When diving tourists come here with cameras to see fish, instead they see garbage underwater, which is not good.
22:40Not only that, fish eat plastic and this also affects humans, as humans eat fish.
22:51With its tropical beaches, the world's fourth biggest freshwater lake is a major tourist destination.
22:58The trash that the divers collect not only threatens Malawi's economy, it's also damaging to the lake's ecosystem, including endemic
23:06freshwater species.
23:08Kenneth Mackay is an evolutionary biologist.
23:13He's observed the impact of pollution firsthand.
23:17Garbage can come on the breeding platforms or in the territories of the males.
23:22Makes it difficult for the fish to breed.
23:24The fish can ingest not only full plastic, but also the microplastic.
23:31And the plastic's breaking down in the lake.
23:34People are drinking it.
23:35So they're going to be getting microplastics.
23:38When people eat contaminated fish, microplastics and toxic chemicals can enter the body.
23:44Scientists say this exposure can affect hormones, reproduction and even the immune system.
23:51In February 2025, the Malawian government officially banned thin plastics, such as food packaging and grocery bags.
23:59But tracking down the producers has proved challenging for the authorities.
24:05Some have changed where they were producing the plastics.
24:09The location where we banned them, that normal production here.
24:13So they changed their production site to relocate to other sites.
24:16So that has also been a problem to regulate and monitor them.
24:21Some of the trash recovered by the divers in Cape MacLear ends up transformed into various products for sale.
24:31We collect garbage like glass bottles, plastic bottles, plastic bags and tins.
24:37We work with these items to recycle them into crafts.
24:47The divers' efforts cleaning up the lake have not gone unnoticed.
24:55When the team collect trash from the water, the water looks clean.
24:59In this way, the fish won't be harmed or destroyed by plastics and glass bottles.
25:03The water is more hygienic, so it's a good idea.
25:08For now, the project is restricted to the Cape MacLear area.
25:12But the hope is that it will inspire further clean-up efforts all over Lake Malawi.
25:19Maybe that is the lesson today.
25:22Before we give up on something, we should take another look.
25:27After all, even an old sack may still have a future.
25:31After all, we should enjoy the air.