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A comparative analysis of quantification and validation methods for prospecting the anthropogenic mine as material reserve for circular construction

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Globally, buildings account for at least 39% of CO 2 emissions and more than 50% of resource extraction and solid waste production. Therefore, any transition to carbon neutral buildings must be paired with new resource sensibilities and a shift from linear models of material consumption to continuous material use within a circular economy. Prospecting the (urban) anthropogenic mine represents an essential step towards circular construction and requires a robust methodology for data collection and interpretation. This paper presents a comparative analysis of survey methods, evaluated by parameters of time, accuracy, equipment, and labor to determine the ability of each tool in providing the necessary data to activate the existing built environment as a material resource. Chosen methods span from on-site manual and analog surveys to off-site digital technologies on a variety of case study scales. In all cases, the output’s data format (sketch book, images, mesh or point cloud outputs) can be cumbersome to process with CAD and BIM software, increasing time to results and limiting the technology’s potential, introducing the call for a new generation of survey tools specifically addressing the needs of deconstruction and salvage in circular construction.
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Journal of Physics: Conference Series
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A comparative analysis of quantification and
validation methods for prospecting the
anthropogenic mine as material reserve for circular
construction
To cite this article: Damun Jawanrudi et al 2021 J. Phys.: Conf. Ser. 2042 012169
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CISBAT 2021
Journal of Physics: Conference Series 2042 (2021) 012169
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doi:10.1088/1742-6596/2042/1/012169
1
A comparative analysis of quantification and validation
methods for prospecting the anthropogenic mine as material
reserve for circular construction
Damun Jawanrudi, Joseph McGranahan, and Felix Heisel 1
Circular Construction Lab, Dept of Architecture, Cornell University, Ithaca NY
14853, USA
1 felix.heisel@cornell.edu
Abstract. Globally, buildings account for at least 39% of CO2 emissions and more than 50% of
resource extraction and solid waste production. Therefore, any transition to carbon neutral
buildings must be paired with new resource sensibilities and a shift from linear models of
material consumption to continuous material use within a circular economy. Prospecting the
(urban) anthropogenic mine represents an essential step towards circular construction and
requires a robust methodology for data collection and interpretation. This paper presents a
comparative analysis of survey methods, evaluated by parameters of time, accuracy, equipment,
and labor to determine the ability of each tool in providing the necessary data to activate the
existing built environment as a material resource. Chosen methods span from on-site manual and
analog surveys to off-site digital technologies on a variety of case study scales. In all cases, the
output’s data format (sketch book, images, mesh or point cloud outputs) can be cumbersome to
process with CAD and BIM software, increasing time to results and limiting the technology’s
potential, introducing the call for a new generation of survey tools specifically addressing the
needs of deconstruction and salvage in circular construction.
1. Introduction
Buildings account for at least 39% of global carbon dioxide emissions [1] and more than 50% of resource
extraction and solid waste production. [2] Therefore, any transition to carbon neutral buildings must
begin with new resource sensibilities and a departure from linear models of material consumption. A
circular economy addresses the negative social, economic and ecologic effects of the current and
dominant take-make-throw model and has been defined as an economy “that is restorative and
regenerative by design and aims to keep products, components, and materials at their highest utility and
value at all times.” [3] The consequent closing of production and consumption loops offers the
possibility to end the loss of valuable finite resources and reduce dependencies on global, volatile
resource markets, support new business models and green job opportunities, prevent greenhouse gas
emissions, and mitigate the effects of the climate emergency. [4]
As global and local actors seek to address climate concerns, the implicit value associated with
embodied carbon, labor, knowledge, and water will impact material valuation going forward. Already
today, the amount of many metals and minerals bound in the built environment has outgrown their
respective naturally occurring reserves. [5] Over the next ten years critical to the effort of restricting
global warming to 1.5 degrees –, carbon emissions from material production, transport, and construction
(embodied carbon) will be responsible for 70% of total new building-related greenhouse gas emissions.
[1] Embedded within a circular economy, circular construction thus calls for the activation of the already
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existing built environment as an anthropogenic mine, a material reserve for the construction of future
buildings. [6]
Unfortunately, the industry has largely failed to documenting material stocks and flows within the
built environment. Consequently, similar to naturally occurring mines, also anthropogenic mines require
careful prospecting in an effort to understand which materials will become available for reuse or
recycling when, and in what qualities and quantities. Detailed documentation represents an essential
step towards circular construction and requires a robust methodology for data collection and
interpretation.
However, the current debate and best practice on single building surveys for demolition or
deconstruction tends to be more anecdotal than quantitative, limiting the potential for informed decision
making. This aspect is especially surprising, when considering the increasing interest in high-quality
datasets and added regulatory requirements on building passports [7] or demolition and deconstruction
audits. [8] In an effort to shift the conversations, this paper provides a comparative analysis of suitable
survey methods for the anthropogenic mine. Following a literature review and methods description in
section 2, section 3 provides an overview of results from several case study buildings. Section 4 finishes
with a comparative evaluation by parameters of time, accuracy, equipment, and labor to determine the
ability of each tool in providing data necessary to activate the existing built environment as a material
resource for circular construction and offers an outlook towards ongoing next steps in the development
of survey tools at the Circular Construction Lab of Cornell University.
2. Tools and survey methods
2.1. Building surveys and reports
Building surveys, formerly known as “structural surveys” [9], are conducted by skilled surveyors for
various reasons and in varying degrees of detail. Most commonly they serve to create measured drawings
of existing buildings and for building value assessment. Typically, building surveys start with research
by the surveyor and then continue moving on site. If there are existing construction documents or
schedules for the structure, these can be used as reference. After assessing the building context and the
building’s exterior the surveyor turns their attention to the interior portion of the building. Finally, the
survey is evaluated and concludes in a report that responds to the specific question of the client. [10]
With respect to circular construction, detailed building surveys provide a foundation for the assessment,
deconstruction, treatment and reintegration of materials and components through reuse and recycling.
Standard equipment for building surveys include measuring tools, paper or tablet for notes and
sketches, a ladder, Personal Protective Equipment (PPE), a device for photographs, binoculars, a
compass, and an electric torch. Whenever the survey exceeds the measuring of dimensions and assesses
materials and their quality or condition, additional equipment is needed such as hammer and bolster,
screwdriver, bradawl and a first aid kit. [10] Next to these common construction survey methods, soft-
and hardware developments resulted in digital sensing tools (e.g. P2P laser distance measurement,
LiDAR or photogrammetry) to perform (non-destructive) architectural surveys, enabling the
quantification of building material content and its quality. [11-13] Following this trend, a recent
generation of mobile tools with these capabilities is now also accessible to every-day users without the
need of specialized equipment. However, questions of applicability, accuracy and compatibility with
existing workflows often remain unanswered.
2.2. Areal or regional surveys and reports
Data sources and methods of data collection in assessing building material content at a regional scale
vary. Top-down methods conduct physical surveys of individual buildings, sampling homes within a
certain time-period and use this information to estimate the urban-mining potential of entire cities. [14]
However, more recent studies have taken advantage of geographical information system (GIS) data to
provide a more accurate, bottom-up methodology of assessing building material content. By applying
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building archetypes to spatialized GIS data, average material stocks at the scale of the building can be
determined. [15-18]
Apart from demolition or deconstruction surveys aiming to evaluate the contemporary state of a
building and its materials after its use, site surveys are also commonly used to assess urban conditions
after natural catastrophes. So-called “damage assessments” estimate the extent of damage and helps
organizing rescue missions. An industry standard for this procedure is Rapid Visual Screening (RVS)
a tool that visually compares and interprets high-resolution satellite images before and after a catastrophe
to quantify damage. [19] The process of RVS is very obtainable and can be learned quickly without
specific prior knowledge. [20] Damage assessment looks at the urban scale, rather than the single-
building scale and is very time sensitive. Therefore, this method serves for rough estimates only with
results that can have big margins of error.
3. Case study survey results and comparison
3.1. Manual on-site survey
A manual, on-site survey of a 3-story 1906 timber residential building in Ithaca, NY was conducted
room by room, utilizing a tape measure to determine the dimensions of each space by measuring the
walls and diagonals where possible. Additionally, ceiling heights, and door and window widths and
location were measured and documented via sketches in a notebook. Following this process, several
walls and ceiling cavities were opened using a hammer and a handsaw to determine the material content
and widths of these sections, which were noted. Stud, joist, and beam spacing was also recorded.
Figure 1. Digital model and material layers created by manual on-site survey.
Taking this information, a detailed 3D model was built using the CAD software Rhinoceros 3D.
The information from opened cavities and documented spacing was assumed to be consistent throughout
the entirety of inaccessible spaces in the building. The translation of the building into a 3D geometry
simultaneously allowed for the calculation and evaluation of the building material content.
3.2. Digital off-site survey
For a pre-demolition material assessment of a church in Auburn, NY, a digital off-site survey has been
implemented based on few personal interior pictures, and publicly available information via Google
maps, street view, and image search. The interpretation and translation of such visual data into a 3D
model was labor intensive and time consuming. This method depends highly on the availability of a
range of pictures or the knowledge of the building elements through plans or a historical context, as
undocumented or hidden elements might be missed, and material quantities underestimated.
Figure 2. Digital model and material layers created by digital off-site survey.
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The resulting model served for a quantitative calculation of various building elements and building
materials. The results are rough estimates with varying precision, based on the available digital data.
The material conditions could partially be estimated through the available images.
3.3. Digital on-site survey
In a second step, a digital on-site survey was conducted at the case study building of section 3.1. Using
an iPad equipped with the photogrammetry app Structure Sensor from Structure SDK, along with the
Structure Sensor Attachment for iPad, 3D scans were taken on a room-by-room basis. With the sensor
having a range of approximately 4 meters, rooms, stairwells, and hallways that exceeded that range were
scanned in multiple parts, as necessary.
In using the scanner, the user should proceed slowly, holding the device approximately 2 meters
from the surface being scanned, panning the device up and down as necessary to capture the ceiling and
floor. When a corner is met, the user should take care to pivot slowly, then continue to follow the surface
of the wall. Following the completion of the scan, an object file (.obj) and material texture file (.mat)
are generated, providing mesh geometry of the environment and a 3D photogrammetry reconstruction.
Following the scan, the mesh geometry contained within the .obj file along with the material texture
can then be imported into Rhinoceros 3D for further processing. Unfortunately, mesh geometry is
considerably difficult to work with in post-processing and requires very labor-intensive steps or newly
developed algorithms for analysis. In a first step, through tracing the mesh, dimensions can be taken.
The mesh can also be split and “unrolled” to communicate the scan via one elevation drawing, both in
geometry and through the photo texture. While this method has obvious limitations with respect to
geometric accuracy, the added information through the embedded image can offer very valuable insight
in evaluation the quality of materials and its conditions.
4. Discussion and conclusion
4.1. Survey method comparison
The comparison of the survey methods in Table 1 clearly shows the benefits and limitations of each
method. Manual on-site surveys show a high accuracy throughout with the downside of labor- and time-
intense work. Digital off-site surveys on the other hand are time efficient but lack in accuracy, especially
with increasing complexity and scale of spaces. They also depend on the availability of digital data from
either online data sources or previous site visits. Often, publicly available data only exists for the
exterior, and not for the interiors of a buildings, which makes this method very unreliable. Construction
documents and bills of quantity from the time of the initial build or a renovation could fill this gap, but
could not be located for any buildings in this study. Finally, the digital on-site survey provides high
accuracy and minimal labor while the cost of technical equipment is high - if not rented. At a lower
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resolution, alternatives in the form of applications on cell phones or tables increasingly make these
methods available to every-day users. For larger scales buildings (large ceiling height, far apart walls),
these methods reach their technical limit, but new generations of hand-held devices not tested by the
authors, such as the iPhone 12 Pro with LiDAR, have the potential to increase the accuracy of these
scans. Regardless of these limitations, digital scanning technologies while efficient on-site still
require intensive post-production due to their output formats, but provide valuable information in respect
to material quality and overall building condition – as well as furnishing and appliances.
Table 1. Comparison of different survey methods in the context of various building types. Scale from
1-5 (best to worst, matching grey scale) describes the relative factor of each individual parameter.
4.2. Conclusion and next steps
While advanced digital technologies can quickly provide a high degree of accuracy and an immense
amount of data points, the same tools often are the most expensive, limiting widespread adoption. Newly
developed tools utilizing smartphones or tablets on the other hand are widely available but reduce
accuracy and compatibility. In both cases, the output’s data format (point cloud and mesh outputs) can
be cumbersome to process with CAD and BIM software, increasing time to results and limiting the
technology’s potential. At the same time, survey methods utilizing 2D data inputs and linear
measurements may be preferable in contexts, where accuracy of dimensions is the highest priority.
Further understanding that goals and available resources between e.g. a city planning authority and a
proactive home-renovator are different, the selection of survey tools and methods is influenced not
solely by merit but other parameters on a case-by-case basis.
With respect to building surveys aiming ease the reintegration of building materials and
components from the anthropogenic mine into new construction, the study shows that there is not one
preferable survey method. Rather, a combination of different tools is required at the moment to generate
the necessary data points to create a detailed material catalogue of all elements in the building, evaluate
these elements for their circularity potential and document connection details and deconstruction
requirements. Lastly, there is currently no available tool to track building elements coming out of
deconstruction in an effort to bridge the gap between demand and supply in circular construction.
Consequently, next steps at the Circular Construction Lab at Cornell University include the development
of (1) a new survey methodology that supports on-site measurements with augmented reality 3d
scanning technologies [21], and (2) the Rhinoceros 3D plugin RhinoCircular, which allows the
immediate calculation and evaluation of circularity potential of materials and connections in 3D
geometries [22].
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Demolition waste represents a significant portion of the total generated waste and has a high importance from both a waste management and a resource efficiency perspective. The urban context is highly relevant to assess the environmental impact of the end-of-life stage of buildings and potential for future reduction to properly design corresponding demolition waste management strategies.The goal of this paper is the development of a framework for the characterization of building material stocks and the assessment of the potential environmental impact associated with the end-of-life of buildings at the urban scale to support decision on waste management strategies. The methodology combines a bottom-up material stock model based on geographical information systems (GIS) and a spatial-temporal database with life cycle assessment (LCA) for the evaluation of end-of-life scenarios.The approach was tested for the city of Esch-sur-Alzette (Luxembourg) and provided significant results on the quantity and the composition of the housing material stock. Two alternative scenarios involving recycling rates of respectively 50% and 70% for inert materials were assessed and an average reduction potential of 25.6% on abiotic depletion potential and 9.2% on global warming potential was estimated.
Chapter
The potential of urban mining is getting greater. From the global view, the potential of urban mining, namely the estimated amount of on-surface stock which has been mine form the geo-sphere into the techno-sphere, is comparative to natural resource which is still in geo-sphere as underground stock. However, practical recycling of metals are still in the stage of developing, and depending on the country. As an example, ultimate potential of urban mine in Japan was estimated. The differences between input of each metal contents and output of it were considered to be accumulated. I/O method was combined to estimate the metal contents in exported products. Japan, which is considered a typical exporter of materials, has great potential of urban mining which comes from domestic demand of products. However, real activity of development of urban mine, namely recycling, is not so effective, especially for minor metals which sometime called rare metals from the viewpoint of the importance in industries. We need to develop the technology and system for urban mining, just now.