Biobased batteries could improve the sustainability of renewable energy grids
The new biobased batteries
Lignode® by Stora Enso is a battery material unlike any we use today. It is a type of carbon that can be fashioned into negative anodes, an integral component of lithium batteries.
Usually, negative anodes in lithium batteries are made from mineral graphite – a problematic material from a sustainability perspective because it is either mined or made from fossil-based substances.
Unlike conventional mined graphite, Lignode graphite is made from lignin – an organic-compounds found inside the cell walls of trees. This makes it renewable and degradable but Stora Enso also goes a step further with its circular manufacturing process. The company only uses pulp by-product from one of its mills to create the material.
Stora Enso is one of the many emerging forestry-based companies trying to push the industry away from its historic association with environmental damage. One way forestry firms are doing this is by innovating in unexpected wood-based replacements for fossil-heavy materials.
Stora Enso is carving out a place for the most traditional of bio-based sectors in the green transition. Its Lignode targets the looming sustainability crisis associated with renewable energy storage infrastructures.
While the renewables transition cannot happen without a ramp up in battery production, these devices are full of toxic, hard-to-extract and hard-to-recycle metal elements: lead-acid (Pb-A), nickel-cadmium (Ni-Cd), sodium-sulfur (Na-S), sodium nickel chloride (NaNiCl2), and, of course, lithium.
As countries expand renewables generation, demand for the precious resources that go into battery production is surging. Argentina, Chile, and Bolivia are stepping up new mining projects at pace. The environmental and social consequences of intensive metals mining is largely overlooked in the rush to supply these valuable commodities.
Lignode opens the possibility of a sustainable renewable energy infrastructure based on biological resources. In recognition of Stora Enso’s achievement, Lignode was selected in 2021 for Finland’s Metsä360 award given to companies strengthening the value of forests.
Lignode is still in its pilot stage but with annual lignin production from Stora Enso’s mill at 50, 000 tonnes per year, all the pieces are in place for scaling. In July 2022, Stora Enso made a commercial breakthrough by entering a joint development agreement with Northvolt, a European supplier of sustainable battery cells and systems. Northvolt will incorporate Lignode to produce sustainable batteries at scale.
Stora Enso’s bio-based carbon material could also prove fundamental to more sophisticated bio-based energy solutions in future. The field of biomimetic battery design is going beyond simply recreating metallic elements from organic compounds, such as Lignode. Rather, it aims for storage solutions that resemble living systems more than inert devices.
Biomimetic batteries replicate or take inspiration from biological mechanisms found inside organisms to store energy. A key candidate right now is the redox system – a series of biochemical processes used to store energy and regulate its flow in living cells.
Because most organic compounds are insulating, biological batteries based on living processes like this would still need inorganic carbon elements inside them to be suitable for large-scale storage. Stora Enso’s tree-based carbon might enable a fully bio-based battery that combines biochemical replicas of cellular energy storage systems with plant-based conductive materials.
Crab, fish and fungi as battery feedstocks
While Stora Enso and Northvolt are busy at work on bio-based negative anodes for the European market, other battery components are still waiting for their bio-based replacements. The most important are electrolytes, positive electrodes, and separators.
LUT University in Finland is where the dream of a fully biobased battery is getting the most focused attention right now. Researchers there are trying to completely reduce our dependence on lithium and in 2023, the institution will invest in a laboratory dedicated to achieving this.
So far, research efforts at LUT have focused on more conventional approaches towards sustainable energy, such as waste metal extraction and re-use. But researchers there acknowledge a more fundamental shift is in order to make the renewable energy transition more ecologically friendly.
“As metal consumption is on the increase, not even a 100% recycling rate would eliminate the need for virgin metals. Moreover, such a recycling rate is impossible to achieve because there is always loss in the collection and recycling process,” says Sami Virolainen, associate professor and head of LUT University’s Department of Separation Science.
In other words, while improving metal recycling techniques is still a worthy goal, the real advance will be to develop bio-based alternatives for every critical component of a battery.
LUT University: The bio-based battery hub
The University of Maryland’s Center for Material Innovation took us one step closer to achieving a fully bio-based battery when it published a recent paper on the uses of chitin for energy storage.
Chitin is a wonder material that is attracting a lot of attention across the biomaterials sector. It is a promising candidate for replacing many petrochemical materials, from plastic packaging to chemicals found in beauty products. This versatile substance is actually one of the most abundant in the natural world – the shells of crustaceans are full of them, as are fungi and insect exoskeletons.
In 2022, University of Maryland researchers reported that is possible to make a firm gel membrane from chitosan that functions as battery electrolytes. This is the battery part that helps ions travel inside the batteries and store energy.
The researchers did not manage to make a fully bio-based electrolyte – their chitosan gel is used in combination with zinc. Still, this marked a huge advance in the field of sustainable battery design.
Zinc is highly recyclable but has so far not been used in rechargeable batteries as they tend to corrode and fail quickly in this application. Adding the chitosan gel inhibited this response, making for a zinc-based electrolyte that was two-thirds biodegradable.
The chitosan-zinc electrolyte battery was 99.7 % energy efficient after 1000 battery cycles. This means that its performance compares very favourably to a typical lithium-ion battery, whose life span is typically 600-1000 life cycles.
The durability of the chitosan battery marks it out as a potential storage method for solar and wind energy, challenging the idea that organic materials necessarily perform worse than mined minerals within electrochemical applications.
The problem with renewables
Developments in bio-based batteries are coming at a critical time for the renewable energy sector.
On the one hand, proponents of renewables have much to celebrate. In 2021, IRENA even reported that two-thirds of newly installed renewable power in G20 countries had lower costs than the cheapest fossil fuel-fired open. On top of this, renewable energy generators like turbines and solar panels are proliferating.
Yet despite signs of an increasingly viable renewables sector, 2022 saw many countries redouble on fossil fuel energy at the first signs of a fuel crisis. The major barrier holding back a wholesale renewables transition is the absence of largescale energy storage.
A 100% renewable energy grid depends on storage technologies in a way that fossil fuels, which can be burned at any time, do not. Wind and sunlight come irregularly so when more energy is generated than the grid needs, the surplus needs to be saved for later release.
The storage system would need to be cost-effective, durable, and capable of retaining large amounts of energy long enough to service peak demand.
Battery storage for renewable surplus is especially important in colder and temperate climates. On a cloudy winter’s day in the UK when solar energy generation would be non-existent and consumer demand high, the country would need at least 1 terawatt hour of electricity.
Against such figures, stats on existing capacity are sobering, with only 34 gigawatt hours available worldwide by the end of 2020. To meet the net zero scenario, we still need to scale up our global energy storage capacity 44 times between now and 2030.
Although there are several types of energy storage, batteries seem the most promising route for solar and wind. It is much more energy-dense than the alternatives, such as mechanical storage more suitable for hydropower. It is also potentially highly scalable.
One thing inhibiting roll out of renewables storage infrastructure is cost. In the UK, the energy company InterGen is building a large new lithium-ion battery storage facility in south-east England for £300 million. Building a whole network of these would easily cost in the trillions.
To accelerate the energy transition, bio-based batteries will need to get cheaper than their metal counterparts and do it quickly. Without significant headway on cost, the biobased battery sector will remain confined to material research laboratories and small suppliers.
However, becoming cost-competitive with ordinary batteries is a tough ask. There is usually a considerable lag between technical breakthroughs in battery design and commercialisation.
At the same time, R&D in bio-based batteries is vital regardless of whether it lowers costs of the tech in the near term. This is because they will become essential to tackle the looming environmental costs of new metal-based renewable energy infrastructures that will arrive over the next decade.
One problem that commercial bio-based energy storage will have to face is the piecemeal nature of the inventions. Right now, bio-based replacements for different battery components are being developed in different institutions and companies around the world. It will take much international collaboration to put these pieces together in a single cheap and marketable model.
