Britain’s Cleantech Startups Are Shaping the Post-Carbon Economy

In the UK, a transformation is underway, one that is reengineering the systems upon which we all rely. From next-generation powertrains and circular packaging infrastructure to domestic lithium supply chains, a wave of cleantech ventures is beginning to reshape some of the most entrenched and carbon-intensive parts of the economy.

Driven by escalating climate policy, shifting capital markets, and rising demand, these companies are no longer pitching marginal gains but working on solutions that will take us into a post-fossil fuel world. 

The UK’s cleantech ecosystem has been bolstered by an increasingly coherent suite of industrial policies, including the Great British Energy Act 2025, which injected £8.3 billion into renewable and grid technologies, and Cleantech for UK, a private-public investment initiative founded in 2023 with backing from then-prime minister Rishi Sunak and philanthropist Bill Gates.

Financially, the sector has matured at pace. The number of dedicated climate funds in Europe has grown fivefold since 2018, and cleantech was the fastest-growing segment in UK venture capital investment in 2024, attracting over £5 billion. The government is aiming for investment worth £35bn in the sector by 2035.

The UK’s Climate Change Committee and National Energy System Operator have both warned that current progress, particularly in clean electricity generation, is too slow to meet net zero timelines. This has placed greater emphasis on technologies that can scale quickly and plug into legacy systems with minimal overhaul.

Sustainable Times’ RISE Awards this November will celebrate outstanding innovators in the cleantech sector. If you're leading a transformative project, we encourage you to apply using the link below.

With thousands of startups driving change across diverse sectors, we've highlighted a few sustainable clean tech start ups who are gaining momentum.

Kvatt: Rethinking the Default in E-Commerce Logistics

One of the more elegant examples is Kvatt, a UK-based startup quietly dismantling the single-use paradigm at the heart of online shopping. Rather than launch a standalone consumer brand, Kvatt has inserted itself into the digital checkout flow, allowing shoppers to opt into reusable packaging with one click. 

Kvatt manages the full return logistics loop distributing, collecting, cleaning, and reusing mailers multiple times, while providing retailers with data on emissions reduction and customer behaviour. Early data shows up to 10% cuts in emissions across partner brands within six months. In a sector where packaging is often considered a sunk environmental cost, Kvatt repositions it as a recoverable asset one that can drive customer loyalty and satisfy emerging regulatory pressure.

The company is also skating ahead of policy. While extended producer responsibility (EPR) schemes inch forward across Europe, Kvatt’s model is already commercially viable. Its potential lies not just in reducing waste, but in nudging e-commerce toward a systemic default  one where reuse is not an exception, but the baseline.

Weardale Lithium: Strategic Minerals, Localised Supply

In County Durham, Weardale Lithium is engaging with an altogether different challenge: how to secure critical minerals for the energy transition without replicating the extractive excesses of the past.

With the UK still importing nearly all of its battery-grade lithium, Weardale’s facility, approved in early 2025, marks a pivot toward sovereign supply chain resilience. The company is converting a former cement works into a geothermal-powered extraction plant, employing direct lithium extraction (DLE) to recover high-purity lithium carbonate from subsurface brine.

Unlike traditional open-pit mining, DLE operates in a closed loop, reinjecting brine and minimising environmental disturbance. Combined with a reliance on local pipelines instead of road transport, the site offers a potential template for low-carbon industrial regeneration, in a region still grappling with the economic aftershocks of deindustrialisation.

What makes Weardale notable is its alignment of place, policy, and planetary need. The project sits at the intersection of the UK’s Critical Minerals Strategy, the push for battery independence, and the wider rethinking of rural economic development. If successful, it will anchor a borehole-to-battery ecosystem that links local geology to global demand.

Carnot Engines: High-Efficiency Power in Hard-to-Abate Sectors

Perhaps the most technically courageous play comes from Carnot, a London-based firm reimagining the internal combustion engine for the post-carbon era. While many in the sector have fixated on electrification, Carnot is targeting fuel-agnostic, high-efficiency thermal engine that can operate on hydrogen, ammonia, methanol, or biogas.

By replacing traditional materials with heat-resistant ceramics and eliminating the need for cooling systems, Carnot claims its engines achieve thermal efficiencies of up to 70%—more than double that of standard diesel. This makes them particularly suited for heavy-duty applications, from marine transport to HGVs, where batteries remain unviable.

What elevates Carnot is a £12.5 million fundraise, strategic investment from Mitsui O.S.K. Lines, and UK government support via the Clean Maritime Demonstration Competition. Carnot’s value proposition is twofold: decarbonisation without compromise, and flexibility in fuel infrastructure transitions. In an era when energy system design is still highly contingent, its platform offers a kind of technological optionality that could prove invaluable.

United by ambition

What unites Kvatt, Weardale Lithium, and Carnot is not their industry, it’s their ambition to restructure the rules of how things move, heat, and circulate. These companies are not just designing products. They are building infrastructure layers for packaging, for minerals, for power designed to persist through policy cycles and trends.

If you are developing the next cleantech company, apply for the RISE Awards. 

Sustainable Times RISE Awards

6 November 2025 at 18:30 – 7 November 2025 at 01:00London

Register Now

Why Apply: The RISE Awards for Cleantech Innovators

The Sustainable Times RISE Awards offer a powerful platform to spotlight breakthrough achievements in the cleantech sector. By participating, your company will gain the opportunity to:

Showcase Your Innovation

Demonstrate how your technology is accelerating the transition to a low-carbon future, whether through energy, mobility, materials, or beyond. Shine a light on your impact, scalability, and vision.

Gain Industry Recognition

Position your company as a leader in cleantech innovation. Finalists and winners will be celebrated across Sustainable Times channels and recognised by top-tier investors, policymakers, and peers.

Build Strategic Connections

Network with over 400 industry stakeholders at the awards ceremony, including climate-focused investors, fund managers, corporate partners, and fellow founders. Our dedicated startup categories ensure high visibility for early-stage ventures looking to scale.

Amplify Your Market Presence

Boost your visibility among mission-aligned backers and customers who are seeking high-impact climate solutions. Let the market see the value and the momentum behind your technology.

Awards Ceremony Information:

• Date: 6th November 2025

• Time:

  • 6:30 PM, Reception Drinks

  • 7:30 PM onwards: 3-Course Dinner, Awards Presentation, and Afterparty with entertainment

• Dress Code: Black Tie

• Venue: De Vere Grand Connaught Rooms, 61-65 Great Queen St, London, WC2B 5DA

The De Vere Grand Connaught Rooms, a Grade II-listed venue in the heart of London's West End, provides a distinguished setting for this event, fostering an evening of celebration and networking.

Sustainable Times RISE Awards

6 November 2025 at 18:30 – 7 November 2025 at 01:00|London

Register Now

We encourage you to consider this opportunity to highlight your team's achievements and solidify your standing in ESG investment, while connecting with promising UK sustainable startups.