Cradle to Cradle Certification: A Peek Inside MBDC's Black Box
"We were looking at our whole sustainability strategy, and we wanted to take it to the next level,” said Richard Guinn, a vice president at Centria Architectural Systems, makers of composite wall-panel systems for commercial and institutional buildings. After researching its options, Centria chose to work with McDonough Braungart Design Chemistry, LLC (MBDC), the Charlottesville, Virginia, company founded in 1995 by architect William McDonough, FAIA, and chemist Michael Braungart, Ph.D.
Known for idealism, vision, and successful consulting with high-profile corporate clients like Ford Motor Company and Nike, McDonough and Braungart have envisioned “a new industrial revolution,” calling for “remaking the way we make things,” the subtitle of their 2002 book
Cradle to Cradle (see review in EBN
). In that book and elsewhere, McDonough and Braungart disparage “cradle-to-grave” products that aren’t designed to be lasting parts of the manufacturing cycle and that poison the environment through pollution and disposal. MBDC’s Cradle to Cradle™ (C2C) protocol envisions every resource used to make products as a safe nutrient in an endless cycle.
In 2005, MBDC launched the C2C Certification Program (see
). Whereas most other product certification standards look at single attributes like recycled content or indoor air emissions, C2C looks at multiple attributes based on cradle-to-cradle philosophy. C2C has certified a variety of building products and materials, from office chairs to piping components to a concrete admixture, as well as consumer items, including a cleaning product and a diaper. As demand for green products grows, so too does the list of C2C-certified products.
Three of Centria’s product lines have joined that list, including its Formawall™ Dimension Series® of insulated metal composite wall panels. As part of its C2C Silver certification, Centria eliminated PVC from the product, created a plan for phasing out other materials identified as hazardous, and identified recycling pathways for the product’s steel and polyisocyanurate foam, among other measures.
However, while the C2C protocol has generated much excitement, the corresponding certification program lacks some of the comprehensiveness and impartiality that are expected in an increasingly sophisticated market for green certifications. This article looks at what C2C entails, how it works, and the role that it plays in the market for green products.
The C2C Standard
McDonough and Braungart often promote three key concepts for environmental design:
waste equals food, use current solar income, and
respect diversity. “Waste equals food” is the conceptual basis for the cradle-to-cradle philosophy that all products should be made using materials that can be recycled indefinitely with minimal environmental impact. McDonough and Braungart use the phrase “current solar income” to argue that manufacturing processes should use energy from the sun or other renewable sources, instead of fossil fuels, which are Earth’s stored solar energy reserve. “Respecting diversity” is about evaluating the impact of industrial processes on all plant and animal life, or, as McDonough and Braungart say, “all the children of all species for all time.”
The C2C certification program works to express these principles through five categories of evaluation criteria. Two deal with the materials contained in a product, and the other three deal, respectively, with energy use in manufacturing, water use in manufacturing, and corporate social responsibility. Based on ratings in each of these categories, a product can be certified by MBDC as C2C Silver, Gold, or Platinum. MBDC evaluates a product in each of the five areas, and its final score is the lowest of its five individual scores. MBDC also performs a more limited evaluation, using only the two materials categories, to certify a simple product as a “technical nutrient” or a “biological nutrient.”
MBDC’s greatest strength and, according to MBDC’s Jay Bolus, executive vice president for certification, “the heart and soul of the program,” is material chemistry. To achieve any C2C certification requires that all ingredients be identified down to the 100 parts per million (ppm) or 0.01% level and assessed according to 19 human and environmental health criteria (see table). MBDC uses these criteria to categorize chemicals with a “stoplight model”—red, yellow, or green. Chemicals with incomplete environmental data are rated gray and are, according to Bolus, treated as if they were red. For a product to achieve any C2C certification other than Silver, it cannot contain any ingredients classified as red—unless red ingredients have no existing substitutes and the manufacturer contains those ingredients in a controlled, closed-loop technical cycle. “You don’t just look at it and say ‘Is it good or bad?’” McDonough told
EBN. “You look at how it is being deployed, and is it contaminating the biosphere?”
C2C’s stoplight model for evaluating chemicals derives from MBDC’s Chemical Profiles Knowledge Database. MBDC has populated this database through years of consulting with product manufacturers, whereby MBDC evaluates chemicals that those companies and their suppliers are using. Clients pay MBDC for its growing knowledge of chemicals based on the database.
2.0 The nutrient cycle
biological nutrients as raw materials that are well suited for either perpetual recycling in industrial systems or beneficial or benign participation in biological cycles. According to Bolus, “The idea is that for something to be truly considered a nutrient, it can be recaptured 100% and has no red ingredients.”
While C2C nutrient certifications, Bolus explained, “are only relevant for very simple things that are homogeneous—such as plastics, fibers, pigments,” all certified products must comply with some level of material reutilization criteria. This category requires that products are designed and manufactured for technical and biological cycles. The standard examines the levels of product recovery as well as use of component materials that are recycled or rapidly renewable and recyclable or compostable at the end of their useful life.
Published C2C literature doesn’t define “recyclable” or “compostable,” but MBDC uses European Union guidelines for biodegradability, Bolus said, and Federal Trade Commission (FTC) guidelines for recyclability. FTC guidelines require an established recycling pathway. However, Bolus told EBN that MBDC might approve a product that falls short of FTC guidelines if the company “has its own takeback program that is available to everyone.”
While MBDC expresses its core expertise in C2C’s two materials categories, it piggybacks on other more established certification protocols in C2C’s three remaining categories. In the areas of energy, water, and social responsibility, a product manufacturer is required to first evaluate its own performance and then progressively increase its compliance with relevant protocols.
The energy criteria focus on the manufacturer’s use of renewable energy to make a product, with a company required to evaluate its energy use for C2C’s Silver certification. Manufacturers need to use renewable energy for the product’s manufacture to achieve Gold certification, and for the energy used in a product’s entire supply chain to achieve Platinum. The renewable energy may be produced either on site or through the purchase of Green-e® certified renewable energy credits.
C2C’s water criteria require companies to work to preserve the quality and supply of water resources. C2C provides a variety of principles and guidelines for companies to work from, with implementation required at the Platinum level.
In its social responsibility section, C2C requires manufacturers to adopt corporate ethics and fair labor statements reflecting company goals. To meet C2C Gold certification, companies must assess their performance against one of several third-party standards supporting fair labor practices, such as SA8000 from Social Accountability International. Companies must satisfy certification requirements under the same standard for C2C Platinum.
What C2C certification doesn’t mean
For someone seeking to understand the meaning of a C2C certification, it may be easy to confuse the cradle-to-cradle philosophy and ideals discussed by McDonough and Braungart with the actual requirements of C2C certification. Sara Graham, sustainable knowledge manager at HOK, told
EBN that based on hearing McDonough speak and reading about his ideas, “I’ve long thought of Cradle to Cradle as the holy grail of industrial process.”
However, there are a number of areas where the concept and the reality of certification—at least at the levels that are being achieved today—don’t match. A C2C Silver certification, for example, doesn’t guarantee that a product is free of all red ingredients—the only “knockout” chemical at the Silver level is PVC. Explaining MBDC’s choice of one knockout chemical, McDonough said, “We specifically focused on PVC because there were so many instances where we could optimize around alternatives.” Although C2C identifies red ingredients at the Silver level, and companies are asked to develop plans to phase them out or optimize them, there is no C2C report card for consumers that details what a certified product does or does not include.
As another example, a certified biological or technical nutrient may not necessarily be returned to biological or technical cycles as the nutrient cycle concept describes. The minimum requirement for certification is merely that a product be 67% recyclable or biodegradable (for details on that calculation, see the sidebar on page 11). Bolus acknowledged to
EBN that the requirement is weak, and explained that in the next version of C2C a product certified as a technical or biological nutrient would have to be 100% recyclable or compostable if it did not contain recycled content.
In addition, even a 100% recyclable or biodegradable product may not be able to return to either the technical or biological nutrient cycle. According to Bolus, “MBDC’s tendency is to certify just the product,” without looking at how it is installed or used. For example, when used as intended, Hycrete, an additive designed to waterproof concrete (see
), is not biodegradable and cannot be recycled by any established process. In practice, then, C2C’s certification of Hycrete as a biological nutrient means that “if you accidentally spill a five-gallon bucket into a local stream, it’s going to degrade and isn’t going to do any harm,” said Bolus.
McDonough has often argued that biological and technical nutrients should be separate or easily separable in a product, and the C2C guidelines do mention “Design for Disassembly.” However, Gabe Wing, a chemical engineer for furniture-maker Herman Miller, Inc., which holds several C2C certifications, said, “We focus on disassembly, but Cradle to Cradle doesn’t spell out” what that should entail for a product.
The FTC recyclability guidelines used by MBDC also do not differentiate between the quality of re-application, or
downcycling, distinctions that McDonough has repeatedly emphasized over the years. In an interview with
EBN he took a softer position on this issue than he has in past speeches. “I think we support all of the companies in the processes they use in moving to cradle to cradle,” he said. “If people can find improved ways to do things, then hallelujah.”
For many of the C2C criteria, Silver and Gold certifications are based on plans and intentions. “Platinum is where the rubber meets the road and they’re actually recovering product,” said Kirsten Ritchie, director of sustainable design for Gensler and an expert on product certification. Tom Lent, policy director of the nonprofit Healthy Building Network, said, “It is pretty important to understand that C2C certification is, at least before Platinum, more about [the manufacturer’s] process with MBDC than actual final accomplishments in the product.” Explaining MBDC’s rationale for the tiered certifications, McDonough said, “People need the opportunity to improve products. We’ve got to give everybody a chance to get into the game, and then we need to test them on their promises.” These distinctions, however, may not be readily apparent to consumers and design professionals, who see the C2C logo stamped on a product, not a process.
Those familiar with C2C philosophy and McDonough’s wide-ranging ideals may be surprised to learn that C2C certification, although covering multiple attributes, is not a comprehensive standard. Lent called C2C a “mixed bag” in its comprehensiveness. C2C’s materials criteria, for example, refer only to the actual product, not manufacturing byproducts or the waste and energy use associated with resource extraction. C2C’s energy- and water-use standards focus on manufacturing, leaving aside energy and water consumption that result from use of a product. There is no assessment of manufacturing air emissions and no assessment of performance or product longevity—all of which can significantly influence a product’s environmental profile. McDonough, while arguing that including criteria on water quality and social issues influenced product design, acknowledged, “We’ve drawn a line around things we’re focused on right now.”
Centria’s Formawall product line illustrates some of the complications with C2C’s certification process. Kynar® is a colorful, durable, and popular choice as an exterior coating on Formawall panels, but as a fluoropolymer its manufacturing process uses—and releases—perfluorooctanoic acid, or PFOA, a bioaccumulative chemical and likely carcinogen (see
). A chemical like PFOA could slip through C2C’s gaps because it wouldn’t be considered in C2C’s materials assessment since it’s not a product ingredient, and while it may be released in water, C2C’s water criteria don’t directly address pollutants. (Guinn told
EBN that MBDC had raised concerns about Kynar but that the specifics stayed between MBDC and Valspar Corporation, the coating supplier.)
Centria also claims that the steel sheets used in its products, as well as the foam infill, are recyclable, but steel coated in Kynar is likely to release toxic chemicals during recycling, and, as a thermoset plastic, polyisocyanurate foam has low value as a recycled material. Formawall panels contribute to a building’s energy efficiency—a benefit that is not considered in the certification—and other environmental attributes have been improved by Centria’s work with MBDC, but it’s hard to see how Formawall could progress beyond C2C’s Silver certification.
There may be other, undetectable, gaps in the system. Outside observers know little about MBDC’s proprietary Chemical Profiles Knowledge Database, with its reputation for comprehensiveness and reliability based on MBDC’s stature in the industry. While McDonough expressed MBDC’s desire to provide the database on a subscription basis, Howell Fendley, project scientist at MBDC, told
EBN that won’t happen “until we can get it more user-friendly—there are now holes in the data and language that is more internal.” Similar reasons were behind the faltering of a prior effort to offer the database by subscription through GreenBlue, the nonprofit McDonough and Braungart founded in 2003 (see
C2C version two
C2C is evolving. Bolus said that a second version would come out in late spring 2007, and, as they do every year, companies will have to recertify to the new standard to maintain their certifications. Version two will address some gaps in C2C, but it will mainly be a revision of existing criteria without fundamental changes, Bolus told
EBN. “We’re going to solicit feedback from companies who have gone through the program” to help guide the revision, he said, adding that he was not sure whether other stakeholders would be consulted.
In addition to strengthening the recycling requirements for nutrient certification, version two will likely add more knockout chemicals that would automatically bar a product from achieving the Silver rating. MBDC will also reevaluate renewable energy credits, said Bolus, and will revisit “materials and water metrics from a global perspective.” Bolus said MBDC has been working with the Business and Institutional Furniture Manufacturer’s Association (BIFMA) and will “add a lot of detail” to the product emissions criteria. “We’re looking to make Silver more stringent,” Bolus added. MBDC intends for C2C to continue as a widely applicable standard: “We’d like to have the logo mean the same thing regardless of what you see it on,” said Bolus.
Manufacturers pay MBDC somewhere from a few thousand dollars to $60,000 for C2C certification. “It depends on how complex the product is,” said Bolus. According to Bolus, about half of the manufacturers who have sought certification first hired MBDC as consultants to help them improve their products. Mark Bonnema, an environmental design engineer for Haworth, Inc., told EBN that when Haworth sought and received Gold C2C certification for specific models of its Zody™ office chair, “we knew where it was because we’d been working with them for a long time.” Bonnema added, “We paid them one price for the consultation and the certification.”
Helping manufacturers drill down
C2C helps companies gain a thorough understanding of what is in their products. Most companies rely on components from other manufacturers. To learn what chemicals and materials are in those components, “they get what is on the MSD [Material Data Safety] Sheets,” said Ritchie. MSD Sheets report chemicals down to 1%–5% material composition and to 0.1% for anything carcinogenic or hazardous. “That’s the standard rule that the supply chain has been working off of, not down to 0.01%,” said Ritchie, “so where is that information coming from?”
According to Bolus, “hard work” is the answer. “We typically rely on suppliers to tell us what they put in the product,” he said. “We do reserve the right to test it if we’re not sure they’re being honest.” A Web-based tool developed by MBDC allows suppliers to enter proprietary information about their production formulas. That information is revealed to MBDC for analysis but not to anyone else, not even the product manufacturer who is the supplier’s customer. In return for participating, suppliers get feedback on which of their ingredients MBDC considers problematic.
Many products have colorants at 100 ppm that are “reds” in MBDC’s database, said Wing. “You find a lot more issues than at the MSD Sheet level,” he said, noting, “You’re deliberately adding ingredients at 100–200 ppm to some plastics, so it is appropriate to drill down to this level.” Wing, as well as representatives of other companies with C2C certifications, said that suppliers usually comply with the requests. “Everybody has their secret recipe,” said Melissa DeSota, who works on the environmental strategy team at Steelcase, Inc., “but they are reassured that they are sharing it only with this third party.” Rick Brow, director of marketing for Centria, agreed: “They were a little reluctant in the beginning, but in the end some of our suppliers took an interest in this for themselves.”
While manufacturers are not required to eliminate all red ingredients to achieve a Silver rating in C2C, companies must create a strategy for phasing out those chemicals in the future. Published C2C guidelines don’t detail what the certification requires of those strategies. ”We will help them develop the strategy and develop some measurable milestones,” Bolus explained. “Let’s say it’s a textile—we might know of some dyes that don’t have hazardous characteristics.” MBDC would share that information and help the manufacturer reformulate its product.
Products must also be recertified each year following review by MBDC. A manufacturer with a C2C-certified Silver product containing brominated flame retardants, for example, would have to demonstrate progress on its plan for phasing out that ingredient. Again, C2C lacks published guidelines on this process. “We look at what they’ve done,” said Bolus. If the company hasn’t eliminated the problematic ingredients, “it’s a judgment call to see whether they’ve made their best efforts,” he said. “We know from our materials experience that there aren’t replacements for some things right now.”
C2C’s requirement that companies engage in an improvement process means that products that otherwise comply with C2C’s requirements could lose their certification if MBDC decides that progress is lagging. “Probably 99% of all companies don’t understand what’s in their stuff,” Bolus said. “The clock starts as soon as they understand what they have, and their certification could get pulled because they don’t make progress on those reds.” So far, Bolus noted, MBDC hasn’t pulled any certifications.
EBN that they value MBDC’s product improvement guidance. “What’s nice about this program is they help us identify areas where we can improve the product,” said Brow. DeSota acknowledged the challenges in removing hazardous ingredients from products but praised MBDC for “doing this type of work and furthering research.” Steelcase’s biggest success with its C2C-Silver Answer® Workstation, said DeSota, is that “there is no PVC in that workstation. We were able to work with one of our vendors to find a non-PVC power and cable solution, which is absolutely huge.”
Is Platinum attainable?
The couple dozen products now certified by C2C include a handful of biological and technical nutrients and a mix of Silver and Gold products—with most companies achieving Silver. No products so far have obtained C2C’s highest rating, Platinum. “Michael Braungart has said that the first Platinum product is probably three or four years away,” Bolus told
While Wing suggested that “on the chemical side it is possible to get there,” Bonnema gave
EBN a few reasons why it would be difficult to go higher than Gold. Bonnema looked at the whole supply chain for the Zody chair to estimate how much renewable energy it would take for Haworth to meet the Platinum requirement. “My first calculation showed that it was a very large dollar number,” he said. “I passed that to MBDC and they said, ‘Wow, we weren’t really expecting that.’ But they don’t necessarily change the certification scheme every time something like that comes up.” Bonnema said he expects the first Platinum to be a simpler product, like a coating.
For Gold certification, Haworth was required to evaluate its performance against a major fair-labor standard like SA8000. “Most reputable North American manufacturers are going to easily meet most of those requirements,” like not using child labor, Bonnema said. However, he added, “The standard places limits on how many hours people can work and on compulsory overtime. North American manufacturing operations are largely built on the ability to flex capacity through compulsory overtime,” a situation he doesn’t believe is likely to change.
Acknowledging hurdles in C2C like SA8000, Bolus emphasized MBDC’s willingness to work with companies. “SA8000 is just one of several programs that we allow—we don’t want to reinvent the wheel as far as social considerations go,” he said. “If there’s something in SA8000 that doesn’t make sense, we’ll try to find some alternatives.”
Developing a certification system is tricky, especially when, as in C2C’s case, its language is closely tied to a philosophical framework that sets such a high bar. MBDC isn’t shying away from that challenge, however. “Platinum is going to be pretty hard to get,” said McDonough, especially for “existing products that were never designed to be that way.” However, portraying the C2C criteria as “a design assignment,” he emphasized that “Platinum products will result from a conscious design choice.”
Some experts, like Ritchie, have questioned whether C2C sets the bar impractically high, while others, like Lent, argue that many of the alternatives set the bar too low. “Many standards that come from collaboration with industry are just the next industry-consented hurdle—a comfortable stretch,” said Lent. “Standards that define an ideal, and rate progress on the way to it, are much more powerful actors for change.”
Multiple attribute programs
MBDC has few peers providing multiple attribute environmental certifications for products, but the field is growing. One of the most comprehensive alternatives is the Sustainable Choice standard from Scientific Certification Systems (SCS), which Ritchie worked on before she left SCS to join Gensler. Sustainable Choice, which includes social factors in addition to environmental ones, underlies both the new NSF-140 sustainable carpet assessment standard and the California Gold Sustainable Carpet Standard. SCS is also developing Sustainable Choice standards for a variety of other product categories. Sustainable Choice is closely related to SCS’s older Environmentally Preferable Products (EPP) program (see
Other organizations active in multiple-attribute analyses include the Institute for Market Transformation to Sustainability (MTS), which has developed a set of sector-specific standards, and BIFMA, which is developing a comprehensive standard that would apply to furniture. In addition, the
GreenSpec® product directory (published by BuildingGreen, Inc., also publishers of EBN), the Construction Specifications Institute’s GreenFormat, and the Healthy Building Network’s Pharos™ Project provide, or are beginning to provide, comprehensive product information, analysis, or screening, if not formal certification.
Key distinctions divide C2C and Sustainable Choice. The Sustainable Choice certification is a transparent standard—the details of the standard are open to the public, and SCS participated in an ANSI stakeholder review process in developing NSF-140, the Sustainable Choice standard for carpets. In contrast, C2C is MBDC’s internally developed proprietary standard. Many aspects of C2C, such as requirements for product improvement processes, are not spelled out in any detail while others, such as the chemical database, are not revealed at all.
C2C’s lack of transparency—it’s perceived as a “black box” of sorts—concerns some observers. “I have every reason to believe that it is a good, rigorous assessment—I just don’t know what that assessment is,” said Pamela Civie, industry research program manager at the State of Massachusetts Toxics Use Reduction Institute. “It is not something I’d discredit but not something we use because we don’t know how they get there,” she added. Stanley Rhodes, Ph.D., president of SCS, commented more bluntly: “No one should buy into a scheme where they don’t know what is under the hood.” Comments by Jason Pearson, executive director of GreenBlue, suggested that C2C is sometimes presented as a panacea, and that the system may need to do more to offer detailed, widely applicable guidance. “It makes it sound like if you’re just smart enough to ask the right questions, then everything else will fall into place like magic,” he said.
MBDC “doesn’t want to go through the ANSI consensus-based process because [we] don’t want to open up to discussion and have [C2C] watered down,” said Bolus. By maintaining direct control, he claimed, MBDC can avoid certifying products that “game the system”—a problem for some certification programs.
Rhodes disagreed with MBDC’s position. “The only way to have a leadership standard is to have it be transparent,” he said. “With carpet, we're dealing with highly technical products that change all the time—you’ll never have outside organizations with the technical expertise to write the standard, so you have to come back to the consensus process.” Knowing that manufacturers and industry groups “are going to water it down,” Rhodes argued for the strategy he said SCS is starting to use—working with industry to decide on specifications and then working with a leading company to set a higher standard that fits the same framework but pushes the industry further along.
Also a concern to some industry peers is that C2C is not a true third-party certification program. Third-party certifications like those offered by SCS are respected by consumers in part because the certifier doesn’t have a financial relationship with manufacturers that could influence the program’s standards or the certification results. According to Ritchie, the standards community is moving toward even greater compartmentalization, “separating the organizations who develop the standard from the ones who do the actual certification.” In contrast, MBDC developed the C2C standard and certifies products with it, while its primary business is consulting with manufacturers. Bolus acknowledged that C2C certification is “really a second-party program.” This interdependence is apparent in Brow’s description of how MBDC looked at Centria’s product formulations. “There is an economic return that is considered,” he added. “It’s not that they want you to go and do something that’s going to put you out of business—the point is to drive you to do the things that are least harmful.”
MBDC is considering having other groups do the majority of the certification work, said Fendley. However, MBDC would retain the final review and authority to issue certifications. MBDC is also considering having an auditor review the C2C certification process, Bolus told
EBN, arguing that this would provide some independent verification that “the process is valid and consistent.”
C2C is distinguished by its translation of inspiring ecological thinking into a real-world product certification system, its affiliation with respected thought leaders, and its idealism. Its usefulness, however, is complicated by lack of transparency, gaps in its underlying criteria at both broad and detailed levels, and the lack of boundaries between the C2C standards-developing body, the C2C certification body, and the MBDC consulting body. Architects and design professionals specifying C2C-certified products may believe that they fulfill McDonough and Braungart’s cradle-to-cradle ideals, without realizing that those ideals are reflected only at the unattained Platinum level.
However, if C2C’s certification raises concerns, MBDC has clearly spurred innovation from its clients. The primary value of C2C certification may be the manufacturer’s consulting relationship with MBDC, with C2C certification providing a way to market that reputation. MBDC isn’t the only certification company with that kind of arrangement—Air Quality Sciences is the only authorized testing lab in North America for the Greenguard Environmental Institute, and it offers consulting services related to the testing it performs for Greenguard certifications. As with companies working with Greenguard, a number of the companies working with MBDC are industry leaders who are known for trying to improve the environmental performance of their products. And while the C2C certification may on its face appear vulnerable to greenwashing, none of
EBN’s sources suggested that the certification was being used to make blatantly misleading environmental claims.
The field of product evaluation and certification systems is young, and C2C’s preeminence may be supplanted in coming years by other systems that surpass it in specificity, transparency, separation of functions, comprehensiveness, and engagement of multiple stakeholder groups. MBDC’s Fendley called for more groups to step up to the task—“It seems that the more companies that are out there doing this, the better,” he said. Said Bonnema, “I think it’s going to be interesting in the next three to five years to see which program or programs in sustainability certification really take off.” McDonough, contrasting MBDC’s present work with his dream of a more ecological nutrient cycle, said, “Right now we’re just trying to get some healthy products out there.”
For more information:
McDonough Braungart Design Chemistry
Roberts, T., & Atlee, J. (2007, February 1). Cradle to Cradle Certification: A Peek Inside MBDC's Black Box. Retrieved from https://www.buildinggreen.com/feature/cradle-cradle-certification-peek-inside-mbdcs-black-box