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Sustainable Reef Starters


OUSD (R&E) MODERNIZATION PRIORITY: Biotechnology TECHNOLOGY AREA(S): Materials/Processes OBJECTIVE: Develop novel carbon-neutral, durable materials to replace traditional gray infrastructure for coastal infrastructure (e.g., seawalls, artificial reefs) to both protect DoD installations and support the development of beneficial coastal ecosystems. DESCRIPTION: Developing novel, extremely durable, and crack-resistant materials for use in the coastal marine environment is of great national security interest. DARPA is soliciting carbon-neutral or carbon-sequestering novel materials that can be used to construct various marine structures, including seawalls, jetties, artificial reefs, and breakwaters, while proving capable of promoting the growth of calcareous organisms (corals and oysters) that form the basis for healthy nearshore ecosystems. Currently, state of the art coastal protection materials require expensive, persistent maintenance (due to storm-induced damage to the structures themselves and degradation of the structures in the seawater environment [1]). Furthermore, the cementitious materials typically used for these structures are not designed to be carbon neutral or negative. The developed carbon-neutral or-negative structural materials should apply recent material science findings or processing techniques to create novel durable products that promote the establishment and growth of calcareous organisms without encouraging macroalgal growth. Materials could include but are not limited to cementitious materials such as marine-, Roman-, or alternative-cement concrete, recycled materials, and novel materials. Solutions must not leach chemicals into the environment that would adversely affect native organisms or, in the case of nitrogen, phosphorus or iron leachates, promote algal growth. Additionally, novel materials amenable to processing techniques that result in unique structural morphologies capable of attenuating wave energy are encouraged. End products should offer sustainable, cost-effective material solutions that can be used to help protect DoD infrastructure while promoting the growth of keystone organisms such as corals or oysters in coastal environments. PHASE I: The materials formulations and associated processing techniques will be developed and refined in this phase. Performers will be required to perform detailed materials characterization using small-batch test samples. At a minimum, the material’s mechanical properties (compressive and tensile strength) and durability in seawater will be determined. Performers must provide a balance sheet showing how their materials can be produced in a carbon-neutral or -negative fashion. Furthermore, materials must be designed to promote the establishment and growth of calcareous organisms while discouraging the growth of macroalgae. An analysis will also be required to ensure that the developed material and processing technique costs are competitive with those for existing gray infrastructure materials and methods. In Phase I, performers will work with DARPA to identify potential transition partners for practical infrastructure testing in Phase II. Performers will begin developing plans with their selected transition partner to scale up their developed material production and processing techniques specific to producing marine structures of interest to the transition partner in Phase II. By the end of Phase I, metrics for proposed field and/or tank testing performance to be performed during Phase II must be established in concert with the transition partner. Phase I metrics: • Achieve a minimum material compressive strength of 25 MPa (after 28 days from preparation for cementitious materials) by the end of Phase I • Demonstrate a material tensile strength of 2.5 MPa (after 28 days from preparation for cementitious materials) by the end of Phase I • Show < 0.20% length change after a test sample is submerged in seawater for 28 days • Document that the material does not leach chemicals that would be deleterious to calcareous organisms and that it wouldn’t promote macroalgal growth • Achieve a carbon-neutral or -negative formulation, as demonstrated through submission of a balance sheet showing carbon emissions and offsets during manufacturing • A proposed cost of the material when produced at scale, as demonstrated via techno-economic analysis of the cost of producing the finished material, in dollars per cubic meter Phase I fixed payable milestones for this program should include: • Month 2: Report on initial material formulation, processing, raw component sourcing • Month 4: Report describing how the developed material’s life cycle is carbon-neutral or -negative and how it is expected to promote calcareous organism settlement and growth • Month 5: Report on the initial material characterization and initial durability seawater exposure test results as well as the material’s compressive strength, tensile strength, and expansion when submerged in seawater • Month 6: Report on carbon-neutral or -negative properties in material composition and manufacturing when scaled-up for full-size, in-water deployment • Month 9: Report on the refined material’s mechanical properties and seawater (28 day) exposure durability test results; and the leachate analysis to support calcareous organism growth while suppressing algal growth • Month 12: Final Phase I Material Design Report summarizing targeted transition partners along with their preferred testing approach and related Phase II metrics, material properties and manufacturing approach, material seawater stability, proposed prototype architectures, data sets, comparison with alternative state-of-the-art methodology, and proposed material costs when manufactured at scale PHASE II: In phase II, performers will demonstrate their concept by scaling up the production of the developed material and associated processing techniques such that the manufacturing chain can be understood and analyzed. The developed material will undergo continued refinement and characterization throughout this phase. Performers must evaluate their material’s mechanical properties and durability in seawater to ensure that the material does not degrade over time or suffer from sulfate or other chemical attack. The material also must be capable of forming, and maintaining when hardened, complex shapes and geometries, either through molds or via 3-D printing techniques, as appropriate. The main goal of Phase II is to move from small-scale laboratory testing to wave tank testing with appropriately scaled structural elements (jetties, seawalls, reef modules, or other wave attenuating substructures) constructed out of the developed material. A second goal includes developing field- or flume-deployed coupons to test the material attraction to calcareous keystone organisms while discouraging macroalgal growth. This second goal will require testing in waters with suitable larval supply for a minimum of 3 months. To achieve the aims of Phase II as specified above, performers will continue to engage with transition partners identified in Phase I as testing advances. The transition partner will work with the DARPA team to select the necessary design for the structure to be fabricated and then tested in the wave tank. Performers must show results of their proof-of-concept structures and testing. Finally, performers will further mature their commercialization plans to include manufacturing scale-up and voice of customer analysis for near- and mid-term opportunities. Phase II Metrics: • By month 12, the performer’s developed material must demonstrate a minimum compressive strength of 30 MPa (after 28 days at 25℃) for cementitious materials), a tensile strength of 3.0 MPa, and show < 0.15% length change after being submerged in seawater for 28 days. The temperature range at which the material is expected to maintain structural integrity and performance must be included. • By month 20, performers must show that native calcareous organisms settled and grew on coupons after a 3-month field deployment (this deployment should be planned with seasonal considerations for larvae availability in the deployment area). • By month 23, achieve the performance metrics identified during Phase I interactions with the transition partner by way of demonstration of a final wave attenuating or other coastal structure tested in a wave tank. Phase II fixed milestones for this program should include: • Month 2: Report on lessons learned throughout Phase I such as material processing and characterization refinements, material formulation improvements or other optimization schemes, and transition partner plan outlining the scale-up and materials processing necessary to form full-size wave attenuating structures • Month 4: Report on the developed materials mechanical properties and stability in seawater • Month 8: Report showing the wave attenuating or wave resistant structural design as defined by transition partner • Month 14: Assessment of structural integrity after deployment of structure prior to flume test • Month 20: Wave tank/flume test of the wave attenuating or other coastal structure; and a report demonstrating that the material attracts calcareous organisms • Month 24: Final Phase II Report summarizing approach; prototype architectures; material properties; material seawater stability; comparison with alternative state-of-the-art methodology; quantification of materials costs and potential location deployments with transition partner PHASE III DUAL USE APPLICATIONS: Structures and the developed materials and processing techniques can be used to help fortify infrastructure and ecosystems (including coral and oyster reef areas) around coastal and estuarine communities as well as DoD/military installations. Work should focus on commercialization of the Sustainable Reef Starters technology. REFERENCES: 1. [1] Gittman, R.K. and S.B. Scyphers, The cost of coastal protection: a comparison of shore stabilization approaches. Shore and Beach, 2017. 85: p. 19-24. 2. [2] Manning, T.J., et al., The Use of Microbial Coatings, Nutrients and Chemical Defense Systems in Oyster Restoration. Marine Technology Society Journal, 2019. 53(4): p. 39-54. 3. [3] Moeller, M., S. Nietzer, and P.J. Schupp, Neuroactive compounds induce larval settlement in the scleractinian coral Leptastrea purpurea. Scientific Reports, 2019. 9(1): p. 2291. KEYWORDS: Materials, carbon neutral, marine structures, reef friendly, coral, oyster, shoreline protection
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