the gold medals are rolling in on the final day of the paris olympics. li wenwen of china has won gold in the women's weightlifting with team gb's emily campbell taking bronze. the stade de france will host the closing ceremony later this evening. now on bbc news: click: sustainability tech this week we have a sustainability special as we revisit some of our favourite sustainable stories

from the last few months. yes, we're up, up, up and away. this plane can stay up in the air almost indefinitely. we're under the ocean with a sd printed sea wall. sustainable leather, anyone? lara's sniffed out a material that's made of beer. doesn't smell of much. a bit like a new car, maybe. and if you don't fancy driving, you could go by rail, where paul's tracking wildlife beside the tracks. love a train. and that is the understatement of the century. let me take you up. up into the air. up above the clouds. above the weather. above all the aircraft. this is the stratosphere.

a place yet to be conquered by humankind. up here the air is thin and calm. and it is here that you'll find the zephyr. this is a strange beast, and the fact that it flies this high is the least strange thing about it. see, it only travels at 40mph. it only weighs 75kg. it's launched by hand. it's completely solar powered. and in theory, it may be able to stay up here for months. i was last at zephyr�*s base in farnborough in the uk in 2018, when it had just stayed aloft for very nearly 26 days. since then it's done 64.

so, this is how it works. during the day, the sun hits the solar panels, which charge the batteries and power the propellers, and the plane climbs to 75,000ft. when the sun goes down, the batteries completely take over. the propellers do slow down and the plane does lose altitude. the trick, though, is to make sure you're still above 60,000ft by the time the sun comes up the next morning, and the process can start again. so will the entire wing be covered with solar cells? every single square centimetre, as much as you can, is solar...? actually, the solar array that we use now typically is so efficient that we don't tend to need to do complete coverage. really? yeah, we can actually recharge the batteries most normal days by lunchtime. spencer laughs wow!

in theory, is it possible to stay up forever in this? well, i think eventually we'll get as close as we can to that. at the moment, our limitation is the number of cycles the batteries can cope with. so a cycle is a day. so a full charge and then a full discharge. that's one cycle. and we're targeting six months in the stratosphere at a time. and that's in line with the battery performance that we see coming through. everything about zephyr has been fine tuned. every gram counts, every unit of battery density. the precise curve of those wings. so, look, i get it. i get that this plane can stay up in the air almost indefinitely. you only have to look at it to understand that it's something pretty special. the main question i have is why? why would you want this kind of craft? who would want this kind of craft? in the 20 years since the idea

was first conceived, it's almost like this has been a solution looking for a problem. would it carry cameras? could it be military? reconnaissance? since airbus spun off the new start—up company aalto in 2023, it's now being pitched for earth observation and as a flying base station for mobile phones. from the stratosphere, at 60 or 70,000ft, we can talk directly to a standard mobile phone, so the aircraft will function exactly like the cell tower that you have today. but it's high up. and because it's so high, so much higher up than the regular cell tower, it can cover the equivalent of about 200 base stations on the ground. so of course, that replaces notjust the, you know, the equipment on the tower, but it replaces the whole tower. that's the steel, that's the backhaul, the fibre, the microwave. very importantly, the power, the electricity or the diesel that runs the tower, and in many cases in remote and rural areas, that's the most expensive part of running a terrestrial tower.

an uplink antenna would connect the mobile network to zephyr, and then zephyr could serve an area of 7,500 square kilometres, in theory for months at a time. this is a real proposition. or, in the event of, say, a natural disaster, a plane could be flown to an area that had suddenly become cut off from the grid. mobile operators have something called cell on wheels, cow, which is usually a truck that has some equipment. we have a cell on wings, a flying cow, which is flying cell on wings. these cows...er, planes will fly autonomously. there are no joysticks involved. the pilots send the plane's coordinates and flight plans, but they're mainly interested in how

much energy it's using and making adjustments to keep its batteries fully charged. so this is the ground and this is 80,000ft. and all this colourful stuff, that's wind. you don't want to be in that. but if you can keep the zephyr above it from about 60,000ft and up, it's pretty plain sailing. the problem is, you've got to get to 60,000ft in the first place, something that can take ten hours from that weird hand launch ta ke—off. |trying to get it up into the air| is probably the trickiest point. there's a lot more weather down ion the surface than there is upl in the stratosphere, so just trying to get| the right conditions to get through that weather, - that's probably the hardest part. we've spent a lot of time and effort studying meteorology in the tropopause, so that we can understand how to transit through it as safely as possible with this aircraft. and we've now done a global study of where all the weather is and all the different weather conditions around the world, and we've found some of the best locations in the world to start launching and landing these from regularly. so where the air is nice

and clear, all the way up... all the way through. yeah. and once we're in the stratosphere, we're away. in fact, zephyr�*s parent company has just announced kenya as the location of its first planned permanent launch site. but we have seen these kind of ventures before. for example, google�*s loon project was also based in kenya, and its balloon—based mobile cell tower project failed to stay afloat. and what about satellites? these days, very small cubesats can be put into orbit at much lower cost than their bigger siblings, and they stay up automatically. no power involved. although, unlike zephyr, you can't bring them down and swap out their payloads. with satellite, if you want to talk to a handset, it's very difficult. and if you manage with low earth orbit satellites, you can talk to a handset, but it would be very limited. you know, it's sms, maybe a few kilobits per second. you cannot do full 56. you're not mimicking what a terrestrial station does.

and if you have satellites that are really big enough that can do something like this, the economics are so expensive, and then you're spreading them across the whole planet. you're not getting the efficiencies. you cannot scale. so that's on the connectivity side. 0n the earth observation side, satellites are great because they can view anywhere on the planet, but not... ..not persistently, because they take an image, come back after a period of time. with high altitude platform stations, you can do that persistently so you can see the change over time. and there is competition in the stratosphere itself. similar aircraft are being developed by several companies, including this one by bae systems. whatever the final use for these so—called high altitude platform stations — haps — there does seem to be both the appetite and now the technology to fly high and stay high.

is this one of the most satisfying bits of tech to watch? but this 3d printer isn'tjust pleasing on the eye. the walls it's creating have the potential to change our impact on the planet. so one of the big challenges of our city, miami, and all coastal cities, is rising sea levels and flooding. and traditionally, cities have addressed this by building sea walls, which you see all around us, even here. and the problem with traditional sea walls is that they destroy marine habitats.

traditional sea walls leach chemicals and, very simply, they're flat. so when you have a flat sea wall, the organisms that live by the coast, they can't attach to this flat surface. so they migrate. and they were the ones who were eating all the toxins in the water. so once the sea life and the organisms migrate, no—one�*s there to eat the toxins. and the quality of water goes down 50% within one year of installation. the challenge for kind designs was coming up with something that was economical for communities, but will also enhance the underwater ecosystem, and they think they've got it. these are the walls that you create. yes. talk us through some of the features. 0k. so, there's three really important features, why these make these walls so great for marine life attachment. 0ne, you have these little micro textures on the wall. and so, if you imagine a rock climber, if they're trying to climb on a flat wall, it's impossible, right? so, same for sea life attachment. thenjust the nature of the 3d printing process. you have all of these layers on the wall. so these layers are great actually for coral growth. and then lastly, you're notjust having your kind of bottom of the food chain on these walls, but because of these caves, you get so much more biodiversity. so every species, their number one

thing is that they want to survive, which makes sense. us too. yeah. us included. and so with these caves, as you can see, they're really deep. i can fit my whole arm in here. so that's where your larger organisms can hide from predators. it takesjust under one hourfor a wall panel to appear before us — much quicker than traditional moulding and setting of concrete. but this way of manufacturing also brings design flexibility. we have the highest resolution 3d printer in the world, so our layers are one inch thick, which allows us to create, like, this design or anything else. and so since we're just producing in florida right now, we're keeping this design. but as we expand nationally and globally, we can alter our design to make it fit

the coastal habitat in any region of the world. you're printing with concrete, which is still one of the most un—environmentally friendly materials there is. are you looking at other materials, or is concrete the only answer here? we are using concrete, one, because concrete sea walls are mandated in many areas. you can use, like, vinyl sea walls, basically plastic sea walls. the problem with them is microplastics are leaching in the water. so also a problem. and two, you can only use them in areas that are very low impact, like a river in orlando or lakes. the difference between traditional concrete and ours is ours is nontoxic, so it doesn't leach. there's no chlorides, there's no metals, and it's also mixed at a 30% lower temperature than traditional concrete, further decreasing the carbon footprint. the start—up are installing theirfirst walls in florida now. studying their impact will be vital in assessing if they make a positive difference and in what direction

the designs will go next. spending billions of dollars to maintain a monopoly. a lengthy battle by the us department of justice. it is unclear what

penalties they will face but it could be forced to break itself apart. alphabet says it plans to appeal the ruling. the royal mint has begun processing large quantities of electronic waste at a new industrial plant to extract gold. the un says 62 million tonnes of e—waste, everything from old phones to laptops are thrown away in 2022. the gold extracted by the royal mint will eventually be used to make commemorative coins. at kernel brewery in

london's bermondsey, something unusual is brewing. this grain, left over from beer production, is commonly used for animal feed or can even end up in landfill, but here it's getting a new lease of life. it's going to be transformed into a leather alternative known as new grain. no animals, no plastic. and now it's time for all of this to head back to arda biomaterials�* lab around the corner. once these sacks arrive at the lab, it's time for the process to begin. first of all, it's emptied out into a container like this, and then an alkaline solution is added. that's stirred for about an hour to extract the protein from the grain. then the husk will be separated and the protein liquid will move along to the next stage, where some natural ingredients will be added. this will be stirred for another couple of hours, and at this point protein strings start to develop, and that means that it's ready to be poured into the trays. now, this tray here has got a pretty smooth finish, so that will create something that looks like a lot of natural leathers. if you want something even smoother than that, well, there's a tray for that too. and for something that's a bit more

of a crocodile look, well, you've even got a version like that. varying the beer that the grain comes from by, say, using stout will result in different final colours. after the material's been sitting in the tray for a day, it's ready to peel off. that's so smooth. that's like pvc. yeah, no... it's completely shiny, cos it's unbacked. and now thatjust needs its sustainable backing added. one of the big environmental issues with leather production is actually the tanning process, though, and arda is hoping for a solution. we are exploring using natural colouring agents, so there's actually a lot of deep tradition in old tanning before the advent of petrochemicals or chromium tanning. so we're exploring these old dyes that are naturally derived and work with the environment and biodegrade. and now for a look at some of the finished product. we've got a whole roll of it here. it looks very much like leather.

this one's quite soft. now, if i smell it, because i know that is the instinct with leather... ..doesn�*t smell of much. a bit like a new car, maybe. these two are made from different types of beer, so the colour is authentic. they do feel less like leather to me, i think because they're harder and more solid. the more flexible ones that are used for something like a handbag feel more like leather, and they've just got that movement to them. on a big sheet here, this could make a bag that would actually fit my laptop, that feels a lot softer. it moves around more like leather does. but i think the main point is, there's a lot of flexibility as to how the finish is going to end up looking and what can be done to it afterwards. there's competition, though. there are lots of other leather alternatives that are coming online, and they each have different positives and negatives. our solution offers a way to scale. do you think it's going to be cheaper than leather? yes. how much cheaper? well, currently a lot

of the breweries we work with at the moment give away their grain for free. so our feedstock is coming in at an extremely low value. some of the bigger breweries sell it. it's quite low. so at scale we calculate that we can undercut leather and plastic leather. and when do you think i'm going to be able to go out and buy a handbag made out of this? um, hopefully this time next year. and it's going to be a cheap handbag? it'll start as a small collection to certain clients and then into luxury, and then slowly moving down the luxury market into more commodity and high street. and what's worth having if there isn't a queue or a waiting list? this is the buckthorne cutting nature reserve,

home to dozens of species of plants, insects and animals. it's hard to believe it's just a few kilometres from the very centre of london, and a technology hot spot. it's a haven of calm and serenity. until this happens. love a train. the area here is based on previously unmanaged network rail land, the body responsible for most of the sprawling railway network in great britain — over 52,000 hectares. they're using a mixture of traditional technology alongside machine learning to identify and monitor wildlife using the space here. so the obvious question has to be, you think of network rail, you think of what we're stood beside — railway lines, trains. why is network rail interested in biodiversity? we've got a massive estate across the whole of britain. it's 52,000 hectares, which, if you squash it all together, is the isle of wight and a half.

and that estate, that network goes through every sort of habitat that you can possibly have. and so we've got that biodiversity on our estate and we can manage it and work with it whilst we're running trains. so i guess with the kind of information that you're collecting, the research that you're doing, how is that beneficial to network rail as a company? what kind of things can you do with that information that you find out? it helps us monitor the condition of the habitats that we've got, so we can use that when we're trying to achieve our biodiversity targets. but it also lets us see what species are using those habitats. and if we know what's there before we come in and do any work, then we can start mitigating for that. we can start, um, doing the work at the right time of year or at the right time of day so there would be less disturbance on those species. the monitoring is being carried out by zoological society of london, or zsl. they're using motion—sensing camera traps to help identify some of the animals. this is a camera trap, and we use this for monitoring wildlife. typically things that move... ..that are kind of larger—bodied and that move along the ground. so we'll typically put it kind

of on a tree around this height. and there's a camera here, and there's a sensor. so if a warm—bodied animal moves past, it will trigger a number of photos. oh, look. that's us. hello! they both laugh in the uk we're using it largely - for ground—dwelling mammals, so, like, foxes and badgers and squirrels, they're really commonly captured, especially in these areas. also, hedgehogs, which is primarily the focus of the london hogwatch group, is looking for hedgehogs. but we also get birds that will stop in front of them if they are on the ground. as well as camera traps, the monitoring team also use specially designed acoustic monitors to capture audio from birds, bats and rodents. and we can listen to all sorts of things. so bats vocalise in ultrasound, so we can't hear it, but we can record it on this and then we can visualise that sound afterwards. it's very, very cool. the same with the dormice. we used it for them as well. and they also vocalise in ultrasound.

really? they sound like, um, like, kind of like a whiny teapot. it's really, really cool. it's crazy. and this little thing picks up all of it? this microphone picks it up. and then also, we use it for, you know, birds. we can hear them right now. while the method of collecting the data may be relatively low—tech, what happens with it afterwards is very much cutting edge. zsl�*s initial pilot project captured 35,000 data files, or 3,000 hours of audio, from just 33 acoustic monitors placed across network rail�*s estate in south london alone. they needed a way to efficiently analyse such large volumes of data, which is where our old friend ai comes in. zsl worked with google, using cloud storage and pre—trained machine learning models, to identify and map species to the network rail estate. back at zsl hq, i sat down with lydia to see some of the results of the analysis.

in some cases there are some really good machine learning models already trained. so for instance, for birds and bats, there are some excellent models out there. and essentially they use these spectrogram images that i'm showing you here. these are really distinctive images. they basically learn these images, which are associated with these different species. the ultimate aim for this research is to understand the true scale of the biodiversity around network rail�*s 20,000km of railway corridor, and advances in technology like this make that more achievable. lara: and that's it for this programme. thanks for watching. we shall be back next week.

hello there. it's a very warm day today but things are going to get hotter for some of us tomorrow. temperatures today are higher than they were yesterday. afternoon temperatures widely into the mid 20s for england and wales. could be reaching 30 degrees in the south—east of england. 0vernight tonight and into tomorrow morning things are going to be changing a bit — for these areas there is a risk of heavy rain, thunder, lightning and some large hail as well. further south, it may well stay dry and for this part of the country, particularly hot and humid. 0ur headline temperature is 35 degrees. that could be reached in cambridgeshire tomorrow afternoon. but for this evening we are going to have some sunshine to end the day for most, but there are one or two thundery showers threatening the south—west. those could drift into wales

and the midlands, more especially into scotland. later in the night we get a spell of noisy weather with some very heavy rain, gusty winds and frequent lightning coming into northern ireland and, later, western scotland. these are the minimum temperatures tonight so an uncomfortably warm night for sleeping. the weather soon cheers up in northern ireland. we get some sunshine. thundery rain pushes quickly eastwards tomorrow morning in scotland. it may affect northern england but it does move away in the afternoon. further south it is likely to stay dry and a much lower risk of the odd shower. more in the way of sunshine and across the midlands and eastern england temperatures will be around 30 degrees or more. 0ut towards the west and north temperatures are going to be lower, as we see fresh air coming in following that spell of wet weather. it has been very hot in spain, and that is where the heat has been coming from. you can see, right the away across western europe, it is to be going to turn cooler over the week ahead as we get atlantic winds coming in. they start to arrive in western areas on tuesday, and we see another band of rain coming into northern

and western parts, with the wind is picking up as well in the north—west. but through the midlands and eastern england it may well be dry still on tuesday, and it is going to be very warm, if not hot. temperatures reaching 28 degrees. again further west things are a lot cooler. after this very hot and humid start some of us, with some sundry downpours in places, the rest of the week will see temperatures gradually falling away, and still rather unsettled.

live from london, this is bbc news. russia says its army will deliver a "tough response" to ukraine's cross—border incursion — as moscow appears to acknowledge that ukrainian units have advanced deep into russian territory. the funeral is being held for nine—year—old alice da silva aguiar — one of three young girls killed in the knife attack in southport. iran's new president announces his cabinet amidst fears of escalation in the middle east.

the final event of the paris olympics is under way, with the united states seeking a historic eighth straight gold in the women's basketball final against france. and banksy strikes again — the elusive street artist confirms he's created his seventh animal—themed piece in london in as many days. welcome to the programme. we begin this hour with the war in ukraine and the country's cross—border offensive. russia says its army will deliver a "tough response" and appears to have acknowledged that ukrainian units have advanced deep into the western region of kursk, saying it's hit troops and equipment around 30 kilometres from the border. it's the most serious attack by a foreign army on russian territory since the second world war. overnight at least two people were killed in kyiv, as russia carried out missile and drone attacks in six regions of ukraine.

louisa pilbeam reports.