The S$6.5 million (approximately US$4.8 million) Carbon Zero Grand Challenge seeks to incentivize innovative solutions that can help PUB achieve net-zero emissions by mid-century and scale to water facilities around the globe. PUB is seeking carbon capture, utilization, removal, and other solutions at any technology readiness level that can be integrated with its operations and reach commercial scale within a decade or sooner.
The grand challenge will have two phases of competition and a pilot-scale demonstration over approximately 45 months. In the Proposal Phase, solvers will submit a detailed proposal addressing net carbon abated, cost, and other critical aspects of their solution. Up to six will be awarded S$250,000 each to develop a Proof of Concept. In the Proof of Concept Phase, solvers will develop a desktop simulation and/or lab-scale study and a detailed design for a pilot project. Up to two will be awarded S$2.5 million each to demonstrate a ~1 kiloton-scale version of their solution at a PUB facility in Singapore.
Click the Guidelines tab to learn more about this challenge and help us take the world’s water to net zero emissions and beyond!
As an island city-state, Singapore’s geography inherently limits its access to natural resources. For this reason, Singapore has always been an innovator and a leader in identifying clean, efficient, and cost-effective solutions for energy, water, and the environment.
PUB, Singapore’s national water agency, manages the nation’s water supply, water catchment, and used water in an integrated way. In 2020, PUB also took on the responsibility of protecting Singapore’s coastline from sea-level rise as the national coastal protection agency.
The Sixth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) that was published in August this year, reinforced the reality that urgent and aggressive action is needed to keep global temperature rise below 2°C, as committed to in the Paris Agreement. Every sector must play its role, including the water sector. That is why PUB has set a goal to achieve net zero carbon emissions by mid-century.
The Carbon Zero Grand Challenge seeks to focus the attention of innovators, investors, and thought leaders on water sector emissions in order to accelerate the deployment of innovative solutions to address Singapore’s net zero carbon emission goals and scale to water facilities around the globe.
Emissions to be Addressed in this Grand Challenge
As an organization, PUB’s emissions in 2020 is approximately 460 kt CO2e as reported in PUB’s Sustainability Report 2020/2021. To achieve its net-zero goal, PUB will need to implement new technologies and solutions to address emissions associated with its water facilities. PUB has built a robust and diversified supply of water, including NEWater facilities that recycle used water and desalination facilities that convert seawater to drinking water (see FIGURE 1).
However, many of these processes are inherently energy-intensive and PUB’s emissions are projected to increase with population rise and economic growth in the coming decades. By mid-century, emissions could double to 1 MtCO2e.
PUB is already working to reduce its carbon footprint by replacing carbon-emitting energy sources with solar PV deployed on facility rooftops and at reservoirs, and reducing carbon emissions through energy efficiency, lowering desalination energy and conservation. These efforts are expected to abate approximately 600 kt CO2e/year of emissions by mid-century.
While current efforts can reduce PUB’s future carbon footprint substantially, PUB is seeking solutions to remove an additional 400 kt CO2e/year associated with its facilities that will require solutions such as carbon capture, utilization and storage (CCUS) and carbon removal (see FIGURE 1 and TABLE 1).
PUB Water Loop
Projected Emissions from PUB
Annual Estimated Projection
Total PUB emissions
1,000 kt CO2e
Emissions for which solutions have already been identified
600 kt CO2e
Emissions requiring new solutions (focus of this grand challenge)
400 kt CO2e
Scope 1 emissions (within emissions requiring new solutions)
200 kt CO2e
Scope 2 emissions (within emissions requiring new solutions)
200 kt CO2e
PUB’s projected Scope 1 emissions that will require new solutions (200 kt CO2e/year) are associated with its four water reclamation facilities and come from two sources:
Approximately 100 kt CO2e/year from anaerobic digester processes that result in an emissions stream containing approximately 35% carbon dioxide; 62% biomethane; and 3% mixed gases that are primarily hydrogen sulfide and nitrous oxide.
Approximately 100 kt CO2e/year of mostly nitrous oxide emissions from nitrification/denitrification that happens in the aerobic wastewater treatment processes.
FIGURE 2 illustrates a typical water reclamation process and the sources of Scope 1 emissions.
Typical Water Reclamation Process and Scope 1 Emissions
The remaining Scope 2 emissions (200 kt CO2e/year) are due to the electricity used to power PUB’s facilities, for example water treatment plants, desalination plants, NEWater Factories and used water treatment plants.
Approaches In-Scope for this Grand Challenge
This grand challenge seeks solutions that 1) directly address emissions associated with PUB’s water facilities, as described in the section above; and 2) have the potential to be deployed at commercial scale within a decade or sooner. Such solutions may include:
Carbon capture, utilization, and storage (CCUS) technologies that can be integrated with PUB’s water treatment or desalination operations
Approaches for addressing greenhouse gas (GHG) emissions associated with PUB’s facilities, while still maintaining PUB’s ambition to achieve energy self-sufficiency through the use of biogas/biomethane generated from anaerobic digestion
Approaches for carbon dioxide removal (CDR), that remove CO2 from the atmosphere that could be integrated with PUB operations
Approaches for carbon dioxide removal (CDR) that remove CO2 from seawater that could be integrated with PUB operations
Any other approaches that directly address emissions associated with PUB’s water facilities and are not out of scope, as described below
Solutions that do not directly reduce or remove GHG emissions associated with PUB’s water facilities are out of scope for this grand challenge. These include:
Approaches to replace grid power used by PUB’s facilities with commercially available renewable power generation sources, such as rooftop solar PV
Approaches involving tree planting, soil sequestration, or similar offset schemes
Approaches addressing any Scope 1 emissions associated with vehicles or travel
Approaches addressing any Scope 1 or Scope 2 emissions associated with building heating or cooling systems
Grand Challenge Structure and Timeline
The grand challenge will focus on accelerating the development of innovative concepts through proof of concept and an initial field demonstration. The grand challenge will include two phases of competition and a pilot-scale demonstration, as follows:
Proposal Phase: Solvers will submit a proposal for their solution, including any relevant data or other credible supporting information; up to six1 will be chosen to move onto the next phase
Proof of Concept Phase: Solvers will develop a desktop simulation and/or lab-scale study based on PUB’s conditions (which will be outlined in the submission template) and a detailed design for a pilot project; up to two will be chosen to develop a pilot project
Pilot Project: Winners from the Proof of Concept Phase will build and demonstrate an approximately 1 kiloton-scale version of their solution at a PUB facility in Singapore and develop a plan to achieve commercial scale within a decade or sooner
The grand challenge will last a total of approximately 45 months, including approximately 21 months for the two phases of competition and 24 months for the pilot project. TABLE 2 provides the expected timeline for the grand challenge.
Grand Challenge Expected Timeline
Grand Challenge opens; Proposal Phase commences
October 19, 2021
Solvers register and develop submissions
October 2021 – February 2022
Proposal Phase registration deadline and submission deadline
February 24, 2022
Proposal Phase evaluation
March – May 2022
Proposal Phase awards announced
Proof of Concept Phase commences; Solvers selected to participate in this phase develop proof-of-concept submissions
June 2022 to March 2023
Proof of Concept Phase submission deadline
Proof of Concept Phase evaluation
Proof of Concept Phase awards announced
Pilot Project, including 6-12 months of operation
Q3 2023 to Q3 2025
1 PUB is seeking to select a variety of solutions that address emissions in different ways to move forward to the Proof of Concept Phase and the Pilot Project Phase. However, the distribution of awards across solutions or types of technology will ultimately depend on the quality of submissions.
Key Performance Criteria
In the Proposal Phase and the Proof of Concept Phase, solvers must address the Key Performance Criteria for this grand challenge, as described in TABLE 3.
Key Performance Criteria for this Grand Challenge
Unit of Measurement
Net carbon abated
The amount of CO2e permanently reduced or removed annually
-Expressed in CO2 equivalent (CO2e)
The projected cost per metric ton of CO2e abated for the solution at full commercial scale (100 kt/yr)
-Expressed in S$/metric ton of CO2e
-Using the techno-economic analysis guidelines explained below
The physical footprint of the solution at pilot scale (approximately 1 kt/year) and at full commercial scale (100 kt/year)
-Expressed in m2
Techno-Economic Analysis Guidelines
For the techno-economic analysis, solvers should provide cost estimates that are reasonably accurate and precise, and presented in such a way that the major cost factors can be broken out and analyzed for error, uncertainty, and sensitivity. The analysis should include all costs over the life of the project on a levelized basis.
Solvers should calculate cost as follows:
S$/tonne of CO2e abated =
(Capital Expense plus Operating Expense minus Revenues)
divided by # of metric tons of CO2e abated
Capital Expense includes materials, equipment, and any other capital expenditures
Operating Expense includes energy, chemicals or other process inputs, personnel, maintenance, and any other operating expenditures
Revenues include proceeds from the sale of any product derived from CO2 captured and utilized by the project
The standard cost of electricity is S$110/MWh
The emission factor for grid electricity is 0.4 kg CO2 per kWh
This grand challenge will offer up to S$6.5 million (approximately US$4.8 million)2 in awards and an opportunity to demonstrate a pilot-scale version of the solution at a PUB facility in Singapore.
Solvers will be selected for an award at the end of the Proposal Phase (up to 6 winners with S$250,000 each) and at the end of the Proof of Concept Phase (up to 2 winners with S$2.5 million each). To receive an award, solvers must accept the Conditions of Contract. See the Conditions of Contract template here. Solvers will not receive the total award funding upfront when the award is announced; rather, solvers will propose (and PUB will need to approve) a payment schedule based on key technical milestones for personnel and reimbursable expenses associated with activities that will be conducted in the subsequent phase. The payment schedule and reimbursable expenses will be part of the submission requirement for each of the two phases of competition.
For example, Solver A is selected for an award based on their Proposal Phase submission. Solver A is now eligible to receive up to S$250,000 over the course of the Proof of Concept Phase. In their Proposal Phase submission, Solver A proposed S$50,000 for reimbursable expenses and two payments for personnel based on technical milestones: one for S$50,000 that occurs when the lab-scale equipment has been set up and one for S$150,000 that occurs when Solver A submits their Proof of Concept Phase submission. If PUB agrees to this payment schedule and Solver A meets both milestones and provides receipts/invoices for the reimbursable expenses, Solver A will receive all payments, totaling S$250,000.
TABLE 4 summarizes the award distribution.
Award Distribution for the Grand Challenge
Total Amount Available
Amount Available Per Awardee
Proposal Phase Winners
X 6 awards
Based on milestones and reimbursable expenses proposed by the solver and approved by PUB; all milestones and reimbursable expenses must be completed by the Proof of Concept Phase submission deadline (March 2023)
Proof of Concept Phase Winners
X 2 awards
Based on milestones and reimbursable expenses proposed by the solver and approved by PUB; all milestones and reimbursable expenses must be completed by the end of the Pilot Project (Q3 2025)
To participate in the grand challenge, solvers must:
Register to compete on the grand challenge website
Complete and execute the Team Agreement
Complete and submit the submission forms below by the applicable deadlines
How do I win?
To receive funding in this grand challenge, solvers must:
Propose a credible budget and milestones
Demonstrate one of the best solutions to be selected for an award
Execute your project plan and achieve your proposed milestones!
Proposal Phase: Submission
All elements of the Proposal Phase submission described below must be submitted by February 24, 2022, at 5:00 pm Eastern Standard Time. Note that any optional supplementary materials that are submitted may or may not be reviewed and considered, at the judging panel’s discretion. All character limits include spaces. Submissions must be submitted using the online submission form.
Section 1: Introduction
Title (50 characters max)
Short Description (140 characters max)
Image (png or jpeg)
Section 2: Company Information: complete if submitting as part of a company
Company name (if any)
Company website (if any)
Date of incorporation (if applicable)
Location of HQ (if applicable)
Which other countries do your company operate in? (if applicable)
No. of employees (if applicable)
Current stage of funding (if applicable)
Section 3: Team Information
Name of contact person
Designation of contact person
Brief description of your key team members
Location of key team members
CVs of key team members
Principal Investigator name, designation, organisation, role/expertise
Covering Principal Investigator name, designation, organisation, role/expertise (if applicable)
Collaborator Team Members name, designation, organisation, role/expertise (if applicable)
Section 4: Your submission
Short Description of Solution: Brief description of the solution that may be shared on the grand challenge website or other public platforms (Do not include any confidential information in this description) (300 characters)
Rationale for the Solution and Innovation
Background of the proposed solution (18,000 characters, image uploads allowed)
Technical description and key features of the proposed solution
Explanation of how the proposed solution addresses the grand challenge and how the solution can be integrated with PUB’s operations
Detailed description of any Intellectual Property (IP) developed and any prior agreements or licenses for the project
Description of the innovative aspects of the solution
Track Record (9,000 characters, image uploads allowed)
Description of relevant past projects, including scope of works and key results
Information on the current state of development for this solution (results of any trials which have been completed to date or successful case studies)
(Optional) Any additional supplementary materials, such as a more detailed techno-economic analysis (Microsoft Word or Excel or PDF Upload; 5 pages maximum for Word/PDF documents and 100MB limit for Excel spreadsheets)
Project Plan - Part 1 (1,500 characters, image uploads allowed)
Total Duration of Project (in months)
Summarize how the project implementation will be carried out and list key objectives.
Project Plan - Part 2 (3,000 characters, image uploads allowed)
List the individual project tasks and their corresponding deliverables. For each task, describe the approach/method to be used.
Project Plan - Part 3 (3,000 characters, image uploads allowed)
Describe the technology development pathway for the solution to achieve full commercial scale in a decade or sooner.
Proposed technical milestones and payment schedule to develop the proof of concept (milestones and reimbursements must be completed by the Proof of Concept Phase submission deadline of March 2023)
Proposal Phase: Evaluation
In the Proposal Phase, solvers will be evaluated on the submission elements described above. The judging panel will consider how well each submission element addresses the goals of the grand challenge (as described in the Background section of these guidelines), as well as the completeness and credibility of each element.
The weightage for each element is as described in TABLE 5. Up to the 6 best solutions will be selected for the award in this phase.
Weightage for each Submission Element in the Proposal Phase
Rationale for the Solution and Innovation
Net Carbon Abated
Development Plan and
Project Budget and Milestones
Proof of Concept Phase: Submission
All elements of the Proof of Concept Phase submission described below must be completed and submitted by the deadline. This deadline is expected to be approximately nine months following the commencement of the Proof of Concept Phase. An exact date and time for the deadline will be posted on the grand challenge website following the announcement of the Proposal Phase awards.
Solvers will follow a template that will be provided after the Proof of Concept Phase commences
Short Description of Solution (Updated): Brief description of the solution that may be shared on the grand challenge website or other public platforms (Do not include any confidential information in this description)
Description/Results of Proof of Concept. This will include:
Lab-scale study or simulation - report that includes data or supplemental information, PUB conditions will be related to outputs of its facilities (solvers may have already demonstrated in other locations)
How solution will be integrated with PUB’s operations
Design for pilot scale - drawings, additional technical details
Proof of Concept Performance. Description of how the proof of concept addressed the Key Performance Criteria for this grand challenge:
Net carbon abated
Development Plan. Plan for demonstrating the solution in a pilot project including:
All project tasks, deliverables, and timeline; and
Assessment of technical and other risks and risk mitigation strategy
Project Budget and Milestones
Detailed project budget including costs related to materials, equipment, personnel, professional fees, and travel to design and develop the pilot project
Proposed technical milestones and payment schedule to develop the pilot project (milestones and reimbursements must be completed by the end of the Pilot Project in Q3 2025)
Description of technology development pathway for the solution to achieve full commercial scale in a decade or sooner.
Proof of Concept Phase: Evaluation Criteria
In the Proof of Concept Phase, solvers will be evaluated on the submission elements described above. The judging panel will consider how well each submission element addresses the goals of the grand challenge (as described in the Background section of these guidelines), as well as the completeness and credibility of each element.
The weightage for each element is as described in TABLE 6. Up to the 2 best solutions will be selected for the award in this phase.
Weightage for each Submission Element in the Proof of Concept Phase
If you're still assembling your submission, you have exactly 8 hours left to complete it!
Here's a Tip: HeroX recommends innovators plan to submit with at least a 3-hour window of time before the true deadline. Last-minute technical problems and unforeseen roadblocks have been the cause of many headaches. Don't let that be you!
There's exactly one week left to submit your solution tothe Carbon Zero Grand Challenge!
You're so close. You can do this!
Remember, the final submission deadline is February 24th at 4:00 pm Eastern Time (New York/USA). No submissions received after this time will be accepted, so make sure to get yours in as soon as possible. Any last-minute questions or concerns can go right in the comments section of this update.
We are pleased to share the winners of Phase 1 of the Carbon Zero Grand Challenge. You can learn about the teams below.
Algae-based Treatment of Anaerobic Digestor Effluent for Carbon Footprint Reduction and Nutrient Recovery, submitted by Rongmo Luo
This project features Gross-Wen Technologies’ leading algae-based treatment system (RAB™) and a leading wastewater solutions provider (Xylem). We propose an algae-based solution to treat anaerobic digester effluent and simultaneously recover nutrients while capturing/offsetting carbon emissions. The approach features CO2 capture by algae, low energy N removal, and reduced nitrous oxide emissions.
Modular & Scalable Emissions Reduction Solution, submitted by Jai Kant Pandit
CO2Tech’s proposed solution combines its energy efficient, competitively lower cost, modular, scalable and compact hybrid technology, HyCaps, with fast catalytic carbon mineralisation. HyCaps takes advantage of the highly selective nature of solvent technology and compactness of membrane technology for CO2 capture. The proposed innovative solution is not only capable of converting CO2 into value added products where CO2 is stored permanently, but is also capable of utilising industrial waste streams including waste from PUB’s desalination facilities to further enhance the techno-economics and efficiency of this solution.