What unsustainable behavior needs to change:

The hotel industry is dealing with a tremendous amount of used towels that need to be washed every day, leading to very high amounts of water consumption. Notably, there has been more and more pressure for hotels from the industry as well as guests, to behave more sustainably. As a result, the question popped up if towels could be reused during one’s stay or if guests need a fresh towel every day. Presumably, trying to engage guests in a towel-reuse program will help to conserve environmental resources such as saving on water and energy. To give an idea, refraining from washing a 10kg towel load saves at least 50 litres of water and 1.2 kilowatt-hours of electricity. 

The Green Nudge:

In 2008, Goldstein, Cialdini & Griskevicius conducted two studies investigating how the hotel industry could increase hotel guest participation in towel-reuse programs. The program is designed in such a way that consumers see a strategically placed card in their hotel room with a specific text, opening them up to think about using their towel again or having it washed. Participation of guests in this program would lead to hotels saving tremendous amounts of water and energy.

The findings:  A card placed in the room with a standard environmental message “help save the environment” led to 37.2% of cases reusing towels. While significant, the study has found that other types of messages can be even more impactful, – particularly, messages  focusing on social influence. For example when using a descriptive norm as in “75% of the guests participated in our new program” this type of signalling appeared to be an effective method. Another example used inviting language to instil more incentive in hotel guests: “Join your fellow guests in helping to save the environment”. Although effective at increasing towel reuse to 44% — even more convincing was when hotels presented guests with a card mentioning other guests’ behaviour in the exact same room: i.e. “75% of the guests that stayed in this room opted to reuse their towels.” This ultimately led to nearly half of the towels to be reused (49,3%). 

This study proved that targeted and place-based social modelling had the most effective nudging.

What unsustainable behavior needs to change:

In the U.S., the widespread practice of pre-rinsing dishes before using the dishwasher stems from ingrained beliefs and poses a significant concern for water conservation. Each pre-rinse consumes up to 20 gallons of water. When scaled nationally, this amounts to an alarming potential wastage of 150 billion gallons annually. In a country where 40 out of 50 states anticipate water shortages and half of the freshwater basins might struggle to meet monthly demands by 2071, such practices demand rethinking.

Several cognitive biases could potentially cloud people’s decision-making processes. Misinformation and a lack of knowledge often lead them to believe that dried-on food won’t come off without pre-rinsing. They can also be influenced by the “anchoring effect,” which causes undue importance to be given to initial information – such as the belief that pre-rinsing is necessary. Moreover, the “effort justification bias” might cause some to rationalise the additional work involved in pre-rinsing. Later, these beliefs are reinforced by the status-quo bias and social norms bias, leading many to adhere to the practice and follow perceived societal norms, thereby perpetuating this water-wasting routine.

The Green Nudge:

The dishwasher brand, “Finish” launched the „Skip the Rinse“ campaign to nudge people away from pre-rinsing. To maximise the reach and impact of their message, they partnered with influential organisations like National Geographic, WWF or The Nature Conservancy.

To debunk the pre-rinsing myth, Finish introduced a gamified approach: the ‚Finish 24-Hour Challenge.‘ Consumers were asked to cook a lasagne, leave it to dry for 24 hours, and then load it into the dishwasher. If their product didn’t completely remove 24-hour dried-on stains, the company committed to covering the cost of the meal. Through gamifying the process, they aimed to challenge existing misconceptions and engage consumers in a fun and interactive way.

The result: The „Skip the Rinse“ campaign has effectively driven behavioural change and aligns with Reckitt’s larger sustainability goals. From 2015, there’s been a 5% decline in their water usage per tonne of production, showing consistent movement towards their 2025 objective. Notably, although manufacturing accounts for less than 1% of their water footprint, a significant 94% comes from direct consumer use. This highlights how campaigns like „Skip The Rinse“ can play a key role in shaping consumer habits, leading to more substantial conservation outcomes.

What unsustainable behavior needs to change:

Toilets are more and more equipped with a dual-flush option. While the design varies widely between different manufacturers, the principle remains the same. There is an option to flush with a full flush (generally supposed to flush faeces) and an option to flush with a partial flush (generally supposed to flush liquids). One of the designs often seen is that of a small and a big button next to each other. While many people have learned to understand that big button =  big flush and small button = small flush, this does not hold true from a nudging point of view. 

Considering that biologically speaking, the small flushing button should be used considerably more often than the big flushing button, the nudging principles of option composition (as identified by Mertens et al. 2022) and more specifically sizing (as identified by Wee et al. 2021) are not adhered to. This is to say that the big flushing button draws more attention than the small button at the generally short decision-making time when picking a flushing button. This consequently leads to excessive use of that big flushing button. Using a full flush with often twice the amount of water as a partial flush when it isn’t necessary is a wasteful use of freshwater and should be prevented as much as possible.

The Green Nudge:

To address this issue right at the moment of decision-making prior to flushing the toilet, Chiel Verstappen developed an interactive prototype known as „The Button Nudger.“

An unmissable message was presented to the toilet user just before flushing: the nudge text (see image) – based on the principle of conveying the norm (as per Byerly et al. 2018),  was humoristic by design and had the added benefit of informing users who are not at all familiar with the dual-flush setup. In users who are familiar, it obviously acted as a gentle reminder to perform a certain action (in this case, consider the small flushing button if it would suffice) as is often the case in nudging. Next to a textual cue, an additional cue based on coloured lighting (centred around the influence of colour on mood/feeling) was given to aid the message. 

The result: The pilot test showed that “The Button Nudger” did have an influence on flushing behaviour. Some toilets showed greater effect than others, with a maximum water reduction of 10.7% and an average water reduction of 6.17%. Taking the average water reduction, a yearly water reduction of 3,180 litres per toilet could be achieved at the University of Twente.

Are you aware of any other nudges that help to conserve water? Feel free to comment or get in touch: hello@green-nudges.com