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The global carbon footprint of medicine is about 5% of global CO2 emissions.1-3 This is quite a chunk of our carbon budget to stay within 1.5° C (2.7°F) of global warming, especially in light that many people globally have only limited access to healthcare. For that reason, countries have pledged to decrease the carbon footprint of their healthcare systems.
So what is the carbon footprint of hearing healthcare? And what strategies and initiatives exist to lower its footprint? The intent of this perspective paper is to start addressing these questions.
To our surprise, disposable Zn-air batteries have a major environmental footprint.4 For example, Ross Dueber, PhD, estimated in 2014 that more than 1.4 billion disposable hearing aid batteries disappear on landfills* around the world each year, and this number at the time was expected to double every 9 years.5** While there are several reasons why disposable batteries will remain a practical choice in hearing aids for some time to come, we can try to reduce their environmental impact. Theoretically, if before 2024, all new hearing aids were to become rechargeable, there would be no demand for disposable hearing aid batteries by 2030.***
The hearing aid industry always has been electrified (i.e., no transition of fossil fuels in that respect is needed). It is known for fast and efficient computing, and cramming as many features as possible into a tiny personal electronic device worn in or at the ear. Specifically designed internal circuits (mini-computers), Low Energy (LE) Bluetooth, and algorithms designed for speed with low computational budget have always played an important role given the limited power allowance and room for electronics available in modern hearing aids.6-8
Until 3 to 5 years ago, most hearing aids were powered by disposable Zn-Air batteries, which were not recycled and sometimes not even disposed of correctly.4 The first generation of rechargeable hearing aids used nickel-metal-hydride (NiMH) technology. It provided benefits to hearing aid users who had difficulty placing a battery in the hearing aid compartment and who now could simply put the hearing aid in a wireless charger. However, the battery capacity of NiMH batteries was limited. In recent years, NiMH batteries have been replaced by superior rechargeable Lithium-ion batteries.9
In December 2021, as an industry first, WSA/Signia published a lifecycle assessment (LCA) in which they directly compared rechargeable lithium-ion hearing aids to an identical pair of the non-rechargeable version.10 The authors showed that the relative environmental impact (use of resources, toxic substances, energy use, etc.) was 65% lower for the rechargeable hearing aids. A quote from the lifecycle assessment:
For the non-rechargeable hearing aids, on average, the battery solution (i.e., production, distribution, and disposal batteries) contributes to more than 80% of the total impacts. For rechargeable hearing aids, on average, the battery solution (i.e., production, distribution, and disposal batteries) contributes to only about 5% of the total impacts. Electricity demand for charging contributes on average 9%. Main contributors are the electronic devices, i.e., hearing aids and charger unit.†
The above lifecycle assessment implies that disposable Zn-Air batteries have a higher impact than the production of the hearing aid itself. However, a point of attention is the long-term capacity of Lithium-ion batteries. In general, the capacity reduces every year by (10-15%), so it’s important to start with a surplus of capacity. A benefit of rechargeable hearing aids not included in the lifecycle assessment is that the number of repairs is lower for rechargeable hearing aids since they are better sealed than non-rechargeable ones. The battery compartment in the traditional Zn-Air batteries is an opening for moist and dirt. If Lithium-ion batteries would be recycled in the future— which now is scarcely done— the environmental benefits may further increase.11
We might also opt for other business models in hearing aid service delivery to decrease our carbon footprint. An example is Whisper AI that provides software updates on their hearing aids.12 Could these updates lead to longer use of hardware and hence less raw materials?
Another point to consider is that if you now buy a new pair of hearing aids, you will in most cases also need to replace your existing accessories including TV-streamer or wireless microphones, since almost every new generation of hearing aid uses new communication protocols sometimes including new connectivity applications. Can’t we go back to the time of universal solutions such as loop systems that were compatible with any brand of hearing aids?
Consumers and the industry would benefit from more standards that facilitate interoperability among devices,. A promising development here is Auracast.13 Another point to discuss among hearing aid manufacturers is a standard charger for rechargeable hearing aids. Best to agree upon an industry-standard early on, instead of waiting until regulators declare a standard as recently happened with the USB-c connector in Europe.14 In some countries that reimburse rechargeable hearing aids, the charger is not included; thus, it will save costs to hearing aid users if previous chargers remain compatible.
Ideally, lower-priced hearing aids will offer rechargeable options as soon as possible. In low- and middle-income countries (LMIC), rechargeable hearing aids might reduce overall costs of use and stimulate sustainable long-term use. We vividly recall one participants’ comments at the Virtual Conference on Computational Audiology (VCCA2020) about how an organization donated hearing aids freely to his community in Africa. He was not particularly happy with the experience since they ran out of Zn-air batteries within a month. This anecdote is not an isolated example. For instance, John Newall and colleagues (2019) reviewed several hearing aid donation programs in the Philippines and found that 20% of the people receiving a hearing aid had difficulties obtaining hearing aid batteries.15
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Charity organizations often provide refurbished hearing aids (i.e., cleaned and serviced devices intended for re-use), meaning those devices do not end on the ever-growing garbage piles but might benefit new users once the original wearer has upgraded to a new device. This raises the question of what the carbon footprint of refurbished hearing aids is (and how rechargeability might affect the equation), as well as the travels abroad associated with donation programs to bring experts to local communities. The carbon footprint of refurbishing a hearing aid was unknown to us at the time of writing.
What we do know is that the success of hearing aid donation programs in LMICs depends on sustainability and long-term follow-up care.15 Frisby and colleagues (2022) demonstrated that community-based hearing healthcare in low-income settings is possible, using Health technologies, achieving a 74% use of hearing aids 6 months post-fitting.16
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How do you calculate the approximate overall carbon footprint of the hearing healthcare industry? One way is by estimating the CO2 impact over the entire lifecycle of one hearing aid (5-10 kg CO2-eq) or Cochlear implant (40-68 kg CO2-eq)20 times the number of devices sold worldwide (18 million).†† Assuming that hearing aids are used approximately 5.5 years, the total estimate of in-use hearing aids amounts to 100 million, meaning that only 1 in 4 persons with disabling hearing loss receives personal amplification.21 From this, a ballpark figure for the total annual direct carbon footprint of the hearing aid industry, excluding bone conduction devices and cochlear implants, is 100-150,000 ton CO2-eq.
For the individual bilateral hearing aid user, the carbon footprint amounts to 10-20 kg CO2-eq and is equivalent to 40-80 kilometers (25-50 miles) driving a medium-sized gasoline internal combustion engine.22 So, driving a car to visit an audiologist may have a higher CO2 impact than purchasing hearing aids. And choosing public transport might be more impactful than choosing rechargeable hearing aids. An upcoming article will discuss how travel habits affect the carbon footprint of hearing healthcare.
Alternatively, one can estimate the total scope 1+2+3 CO2 emissions over the entire value chain of the biggest corporations within the hearing healthcare industry. Scope 1 includes all direct emission from an organization’s core activities, Scope 2 includes indirect emissions that result from the generation of purchased or acquired electricity, heating, cooling, and steam consumed by an organization, and Scope 3 includes indirect emissions not included in Scope 2 that occur outside of the organization in the supply chain.23 Using the data reported by the seven largest corporations, summarized in Table 1, we get an estimated total yearly emission of 1.9-2.3 million ton CO2-eq.††† For the hearing healthcare industry, it would cost around $190-230 million to compensate for the CO2 emissions by buying CO2 allowances (current market price $100 per ton) in a gap and trade system, based on rates from the EU ETS which can be bought via Carbonkillers or the Compensators.24,25
We hope that soon every hearing aid manufacturer performs lifecycle assessments on their products and even employs a Sustainability Officer, as WSA/Signia and Sonova have done. Besides the carbon footprint, we should not forget other environmental factors such as use of raw materials, toxic waste, rate of refurbishments (re-use), recycling rate, packaging, and transport.17
New hearing aids will not only be praised in marketing for their better performance compared to previous generations, but also for their reduced environmental impact. As a consumer, you can consider rechargeable hearing aids. As a field, we may set an example within medicine by phasing out disposable Zn-air batteries, increasing the overall recycling rate to 70% by 2025, and striving for carbon neutrality of scope 1+2 emissions before 2030, while serving more hearing impaired people.
We want to thank Ross Dueber, Lisa Clive, Stuart Bowen, Mariana Villar, Chaojun Li, Stefan Launer, De Wet Swanepoel, Tarien Swanepoel, and Veronika Abraham for providing information and advice while we were writing this article.
* In the US most disposable batteries do end up on a landfill. However, in many West-European countries, batteries are collected and disposed properly or recycled if possible. A growing number of Zn-Air batteries is recyclable and due to concerns on environmental impact no longer contains mercury.
** In personal correspondence Dueber explained he made his estimation based upon global annual sales, the average life of a hearing aid, and average days between battery replacement. Other environmental factors are paper and plastic packaging of the batteries and their transportation cost. The growth rate of battery use may have decreased since then because of adoption of rechargeable hearing aids.
***Assuming an average life-time of 5.5 years for a hearing aid.
† The absolute environmental impact depends on many local contextual factors, including the hearing aid model, user profile, years of use, electricity mix of renewables for charging, etc. Minimal environmental impact is achieved by maximizing the use phase, using green energy, and preventing waste wherever possible.
†† Based on estimates provided by Bernstein, WSA/Signia, Sonova, and Cochlear. The exact carbon footprint depends on many factors, including the region where it’s produced, rechargeability, and energy mix of the power grid.
††† Based on the ESG reports by Sonova, Demant, WSA/Signia, GN Resound, and Cochlear. Excluding Starkey and MED-EL which are privately owned and did not report on environmental policies. Therefore, we added a 20% margin.
Jan-Willem Wasmann, MSc, ist ein medizinischer Physiker und Audiologe am Radboud University Medical Center (Radboudumc) in Nijmegen, Niederlande, und spezialisiert sich auf die Identifizierung, Diagnose, Behandlung und Überwachung von Störungen des auditorischen und vestibulären Systems des Ohres.
Jan de Laat, PhD, ist ein Physiker-Audiologe am Universitätsklinikum Leiden in Leiden, Niederlande, der die psychologischen und psychosozialen Aspekte von Hörverlust untersucht.
