A completely clean, renewable energy system that can be produced locally and that can easily power heat, energy storage and transportation, and travel — that's the future that promoters of a hydrogen economy envisage.

If it sounds a bit like rocket science, that's because it is. Hydrogen is what's used to fuel rockets — that’s how powerful it is. In fact, it’s three times more powerful as a fuel than gas or other fossil-based sources. And, after use, it’s frequently converted to drinking water for astronauts.

US President Joe Biden has highlighted the potential of hydrogen in his ambitious plans for economic and climate recovery and a number of recent reports have been encouraging about hydrogen’s breakthrough moment, including McKinsey and Company (Road Map to a US Hydrogen Economy, 2020) and the International Energy Agency.

Hydrogen fuel cells provide a tantalising glimpse into our low-carbon future

The McKinsey report claims that, by 2030, the hydrogen sector could generate 700,000 jobs and $140bn in revenue, growing to 3.4 million jobs and $750bn by 2050. It also believes it could account for a 16% reduction in CO2 emissions, a 36% reduction in NOx emissions, and supply 14% of US energy demand.

So how does it work?

Simply put, hydrogen fuel cells combine hydrogen and oxygen atoms to produce electricity. The hydrogen reacts with oxygen across an electrochemical cell and produces electricity, water, and heat.

This is what gets supporters so excited. In theory, hydrogen is a limitless, incredibly powerful fuel source with no direct emissions of pollutants or greenhouse gases.

So what's the problem?

Right now, there are actually a few problems. The process relies on electrolysis and steam reforming, which are extremely expensive. The IEA estimates that to produce all of today’s dedicated hydrogen output from electricity would require 3,600TWh, more than the total annual electricity generation of the European Union.

Moreover, almost 95% of hydrogen currently is produced using fossil fuels such as methane, natural gas, or coal (this is called "grey hydrogen"). Its production is responsible for annual CO2 emissions equivalent to those of Indonesia and the United Kingdom combined. In addition, its low density makes it difficult to store and transport — it must be under high pressure at all times. It’s also well-known for being highly flammable — its use as a fuel has come a long way since the Hindenburg Disaster but the association still makes many people nervous.

A Hydrogen refuelling station Hafencity in Hamburg, Germany. Infrastructure issues must be addressed if we are to see more hydrogen-fuelled vehicles on our roads. | Image credit: fritschk / Shutterstock.com

So there are quite a few problems. What’s the good news?

In the last few years, we've seen how rapidly investment, innovation, and infrastructure policy can completely transform individual renewable energy industries. For example, the IEA analysis believes the declining costs of renewables and the scaling up of hydrogen production could reduce the cost of producing hydrogen from renewable electricity 30% by 2030.

Some of the issues around expense could be resolved by mass manufacture of fuel cells, refuelling equipment, and electrolysers (which produce hydrogen from electricity and water), made more likely by the increased interest and urgency. Those same driving forces could improve infrastructural issues such as refuelling stations for private and commercial vehicles, although this is likely to require coordination between various stakeholders, including national and local governments, industry, and investors.

The significant gains in renewable energy mean that “green” hydrogen, where renewable electricity powers the electrolysis process, is within sight.

The IEA report makes clear that international co-operation is “vital” to progress quickly and successfully with hydrogen energy. R&D requires support, as do first movers in mitigating risks. Standards need to be harmonised, good practice shared, and existing international infrastructure built on (especially existing gas infrastructure).

If hydrogen can be as efficient and powerful a contributor to a green global energy mix as its proponents believe, then it's better to invest sooner rather than later. If that investment can help power a post-Covid economic recovery, even better.

The world’s biggest ever survey of public opinion on climate change was published on 27th January, covering 50 countries with over half of the world’s population, by the United Nations Development Programme (UNDP) and the University of Oxford. Of the respondents, 64% believe climate change is a global emergency, despite the ongoing Covid-19 pandemic, and sought broader action to combat it. Earlier in the month, US President Joe Biden reaffirmed the country's commitment to the Paris Agreement on Climate Change.

It is possible that the momentum, combined with the difficulties many countries currently face, may make many look again to geoengineering as an approach. Is it likely that large scale engineering techniques could mitigate the damage of carbon emissions? And is it safe to do so or could we be exacerbating the problem?

The term has long been controversial, as have many of the suggested techniques. But it would seem that some approaches are gaining more mainstream interest, particularly Carbon Dioxide Removal (CDR) and Solar Radiation Modification (SRM), which the 2018 Intergovernmental Panel on Climate Change (IPCC) report for the UN suggested were worth further investigation (significantly, it did not use the term "geoengineering" and distinguished these two methods from others).

One of the most covered CDR techniques is Carbon Capture and Storage (CCS) or Carbon Capture, Utilisation, and Storage (CCUS), the process of capturing waste carbon dioxide, usually from carbon intensive industries, and storing (or first re-using) it so it will not enter the atmosphere. Since 2017, after a period of declining investment, more than 30 new integrated CCUS facilities have been announced. However, there is concern among many that it will encourage further carbon emissions when the goal should be to reduce and use CCS to buy time to do so.

CDR techniques that utilise existing natural processes of natural repair, such as reforestation, agricultural practices that absorb carbon in soils, and ocean fertilisation are areas that many feel could and should be pursued on a large scale and would come with ecological and biodiversity benefits, as well as fostering a different, more beneficial relationship with local environments.

A controversial iron compound deposition approach has been trialled to boost salmon numbers and biodiversity in the Pacific Ocean.

The ocean is a mostly untapped area with huge potential and iron fertilisation is one very promising area. The controversial Haida Salmon Corporation trial in 2012 is perhaps the most well-known example and brings together a lot of the pros and cons frequently discussed in geoengineering — in many ways, we can see it as a microcosm of the bigger issue.

The trial deposited 120 tonnes of iron compound in the migration routes of pink and sockeye salmon in the Pacific Ocean 300k west of Haida Gwaii over a period of 30 days, which resulted in a 35,000km2, several month long phytoplankton bloom that was confirmed by NASA satellite imagery. That phytoplankton bloom fed the local salmon population, revitalising it — the following year, the number of salmon caught in the northeast Pacific went from 50 million to 226 million. The local economy benefited, as did the biodiversity of the area, and the increased iron in the sea captured carbon (as did the biomass of fish, for their lifetimes).

Small but mighty, phytoplankton are the laborers of the ocean. They serve as the base of the food web.

But Environment Canada believes the corporation violated national environmental laws by depositing iron without a permit. Much of the fear around geoengineering is how much might be possible by rogue states or even rogue individuals, taking large scale action with global consequences without global consent.

The conversation around SRM has many similarities — who decides that the pros are worth the cons, when the people most likely to suffer the negative effects, with or without action, are already the most vulnerable? This is a concern of some of the leading experts in the field. Professor David Keith, an expert in the field, has publicly spoken about his concern around climate change and inequality, adding after the latest study that, "the poorest people tend to suffer most from climate change because they’re the most vulnerable. Reducing extreme weather benefits the most vulnerable the most. The only reason I’m interested in this is because of that."

But he doesn't believe anywhere near sufficient research has been done into the viability of the approach or the possible consequences and cautions that there is a need for "an adequate governance system in place".

There is no doubt that the research in this field is exciting but there are serious ethical and governance problems to be dealt with before it can be considered a serious component of an emissions reduction strategy.

Gardens and parks provide visual evidence of climate change. Regular observation shows us that our flowering bulbous plants are emerging, growing and flowering. Great Britain is particularly rich in long term recordings of dates of budbreak, growth and flowering of trees, shrubs and perennial herbaceous plants. Until recently, this was dismissed as ‘stamp collecting by Victorian ladies and clerics’.

The science of phenology now provides vital evidence that quantifies the scale and rapidity of climate change. Serious scientific evidence of the impact of climate change comes, for example, from an analysis of 29,500 phenological datasets. This research shows that plants and animals are responding consistently to temperature change with earlier blooming, leaf unfurling, flowering and migration. This scale of change has not been seen on Earth for the past three quarters of a million years. And this time it is happening with increased rapidity and is caused by the activities of a single species – US – humans!

Iris unguicularis (stylosa). 

Changing seasonal cycles seriously affects our gardens. Fruit trees bloom earlier than previously and are potentially out of synchrony with pollinators. That results in irregular, poor fruit set and low yields. Climate change is causing increased variability in weather events. This is particularly damaging when short, very sharp periods of freezing weather coincide with precious bud bursts and shoot growth. Many early flowering trees and shrubs are incapable of replacing damaged buds, as a result a whole season’s worth of growth is lost. Damaged buds and shoots are more easily invaded by fungi which cause diseases such as dieback and rotting. Eventually valuable feature plants fail, damaging the garden’s benefits for enjoyment and relaxation. 

Plant diseases caused by fungi and bacteria benefit from our increasingly milder, damper winters. Previously, cooling temperatures in the autumn and winter frosts prevented these microbes from over-wintering. Now they are surviving and thriving in the warmer conditions. This is especially the case with soil borne microbes such as those which cause clubroot of brassicas and white rot, which affects a wide range of garden crops.

Hazel (Coryllus spp.) typical wind-pollinated yellow male catkins, which produce pollen.

Can gardeners help mitigate climate change? Of course! Grow flowering plants which are bee friendly; minimise using chemical controls; ban bonfires – which are excellent sources of CO2; establish wildlife-friendly areas filled with native plants and pieces of rotting wood, and it is amazing how quickly beneficial insects, slow worms and voles will populate your garden.

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Professor Geoff Dixon is the author of Garden Practices and their Science, published by Routledge 2019.