Asia’s First Green Roof Bus - Observatory of Public Sector Innovation

This innovation represents Asia’s first public bus with a live green mat on top. The Green Roof Bus was developed for:

1. Awareness: To remind people of the flora and fauna that are sacrificed for dozens of new building. By using public transport, the outreach was wider and also serves to remind the public that public transport greatly reduces your carbon footprint versus owning a car.

2. Bus temperature reduction: both internal and external and in turn, reduction of fuel consumption.

Innovation Summary

Innovation Overview

GWS Living Art took the opportunity to take part in the Temasek Ecosperity challenge with our ‘Green on the move’ concept. GWS Living Art has a long-standing track record in green roofs but we felt that more could be done. We wanted to further test the green roof to benefit the larger community through public buses. We were inspired by billboards on buses and wondered if we could design a system for mobile green akin to a billboard. After going through many rounds of discussions and involving different stakeholders, these green-roofed buses finally came alive in May 2019. Other partners supporting this initiative include Singapore’s SBS Bus Transit, MooveMedia, National Parks Board (NParks), and Singapore Green Building Council (SGBC).

Asia’s First Green Roof bus is a mobile green roof installed on a public bus. The green roof, a green building product certified by the Singapore Green Building Council’s Singapore Green Building Product certification scheme, is made up of Sphagneticola trilobata and other hardy plants adapted to the local climate, chosen for their resistance to windy and dry conditions. Instead of conventional soil, the plants are secured using GWS’ proprietary Gaiamat, a lightweight mat used for skyrise greenery that is cleaner, easier to maintain and more economical than other conventional green roof systems which are primarily soil-based. The mat is also easy to install and easy to maintain, so that it can be easily extended to more buses.

In total, we had 8 single deck green roof buses going around various routes in Singapore and 2 control buses. In total, these 10 buses formed part of a research study, also supported by Temasek Foundation, to explore the link between green roofs and the interior temperatures of the buses, focusing on quantifying the reduction in heat transmission on vehicular roofs due to the addition of rooftop greenery. The aim of our three-month study was to test if and how much the green roof will lead to a drop in temperature within the interior of the buses, and assess a reduction in the fuel consumption used for air-conditioning. A significant drop can have a huge impact on Singapore’s bus fuel consumption and with that, public transport just became even more carbon footprint friendly. Our nation has an extensive public transport network and the benefits would be to more than just one segment of people.

Our vision is for all buses to have a green roof and perhaps even seeing bio-diversity on our roofs. Our mat system is patented and we have also developed the method statement for easy installation. As many countries has a similar single deck bus, we believe this is scalable. We also plan to refine the installation method such as that it will weigh lesser and we will be able to enhance the size of the green roof on the bus roof. We are grateful for the support we have received from our stakeholders in Singapore and we believe their endorsement would help to scale this innovation as well.

Innovation Description

What Makes Your Project Innovative?

Our project is Asia’s first green roof bus. We have also tried and tested this plant species such that it is able to thrive in most of Southeast Asia’s humid and tropical climate. While the Cyanotis Cristata is very resistant, the Wedelia Trilobata helps to absorb CO2. Our system does not require soil thus the whole process is cleaner and can even absorb rainwater. This translates to a hassle free maintenance for the bus operator as well. The installation was also a first for us as we made many trips to Moovemedia to design how our green roof will be attached on to the bus securely. We also catered for windy situations to ensure that nothing will latch onto the green roof.

What is the current status of your innovation?

The first Green Roof Bus was completed in May 2019. In August 2019, all buses have started on their routes with the green roof. We have concluded the 3 month research in December 2019 on the effectiveness of the green roof to reduce the temperature and fuel consumption. The results are significant, for a full solar radiance the green roof can reduce 12C on the surface of the bus roof, and 8C on the surface of the roof inside the bus. This results have surpassed the target of our hypothesis, which is 5C.

As for the energy reduction for the bus as a result of the reduction of the temperature, we will have to do further tests such as heat flux within the buses, and we are in talks with a few government bodies to implement such research projects.

Innovation Development

Collaborations & Partnerships

1. Temasek Foundation : Funding Support and organizer of the Temasek Ecosperity Liveability Challenge
2. Singapore Green Building Council: Certification, Press coverage and media launch
3. Moovemedia & SBS Transit: Bus Operator, installation and logistic as well as Billboard design
4. National Parks Board Singapore: Media Coverage and launch support
5. National University of Singapore: Research Report and support from Professor Tan

Users, Stakeholders & Beneficiaries

User & beneficiaries: Citizens
The public response was good as people were intrigued by this creative innovation and it reinforced what we knew, that people will always be drawn to nature. They report sightings of the buses and happy that we are all working towards a greener city.

Main Stakeholders: Temasek Foundation
Value add to the Foundation's ecosperity projects – Supporting sustainable and innovation solutions to improve liveability.

Innovation Reflections

Results, Outcomes & Impacts

After installing both indoor and outdoor sensors, temperature differences were taken for typical days with clear sky conditions and overcast sky condition. Sky condition and temperatures were based on a weather station.On a typical clear sky day, peak temperature is observed at 14:00 hrs. The surface temperature reduction due to green roof is ~14.56 °C, interior surface temperature reduction is ~16.02 °C . On a typical day with overcast sky condition, peak temperature observed at 15:00 hrs. The surface temperature reduction due to green roof is ~13.65 °C and interior surface temperature reduction is ~9.1 °C. For rainy day, peak temperature reduction is ~2.76 °C and interior reduction is 2.8 °C. Empirically, surface temperature of bus rooftop surfaces can be reduced by ~12 °C on the exterior and 8 ºC on the interior during peak solar irradiance when a green roof is installed. Full impact not captured as methodology do not extend to related aspects of green (eg. air quality).

Challenges and Failures

As this is the first time the bus operators are exploring this, the challenge was in installing the sensors. We had initially placed it at the interior ceiling of the bus however it had to be moved once and this might have affected a part of the results and some data could not be used for analysis. Our aim was to place the interior sensors at the same spot where the exterior sensor was. Fortunately, we had sufficient data for analysis given we had 8 buses and 2 controls buses.

Secondly, there was unavailability of stationary buses that we were able to use as control buses. Our control used were buses that were moving but had no green roof. Ideally, we would have wanted to have stationary buses that had green roof on it as well for a more robust analysis.

Conditions for Success

A large part of our success came from supportive policies and leadership. Our stakeholders played a part in the outreach and support for this project and as we are using one of the 3 bus operators in Singapore, a consensus between stakeholders is necessary. We also had guidance for the media launch and this aid in raising awareness for the public to lookout for the green roof bus. Financial resources is also necessary. GWS Living Art developed the patent for the green roof mat system and brainstormed with Moovemedia for the installation. However, the bus space rental was financially supported by Temasek and Moovemedia. Financial resources are necessary as the report would need a minimum of 8 -10 buses for us to conduct a thorough analysis. Looking back, time is a necessary condition for this research. We required more time to expand our research into testing the reduction of fuel consumption and energy and collection of this data required more support.

Replication

There is huge potential given that majority of countries use a similar single deck bus. The installation method is not proprietary and GWS Living Art is the manufacturer and supplier of our GWS Green Mat system which can be rolled up and shipped internationally. The difference would lie in species of plants as our current system is catered for the tropical climate. The plant species used are Cyanotis Cristata (resistant plant) and Wedelia trilobata (able to absorb CO2). With more recognition of the Green Roof Bus, it would be critical in influencing of other governing bodies in the region. We believe that this is critical in inputing more carbon sinks within our world, and increasing spaces for bio diversity as well.

Lessons Learned

No idea is too small to change the world. Sustainability is now more than just a lifestyle – it needs to be a priority for cities and citizens. One green roof bus might be small in size but the impact will be felt when all the buses have green roofs on them one day. As cliché as it sounds, setbacks are and will always be a part of the journey. To get approvals from the statutory boards, we had to constantly refine our installation method and our system as each national statutory board brought up an issue we had to solve and account for. The Ministry of Environment and Water Resources brought up the issue of pests. We had to modify our maintenance to cater for this. We also learn that the additional weight from the green roof would affect the fuel consumption reduction. There was also an issue with the data extraction for fuel consumption. Many of these factors resulted in a time lag for the project. However, it only served to better the quality of our innovation.