As
cities continue to grow rapidly and multiply across developed and emerging
markets, managing their use of materials becomes a task of vital importance for
civilization. Cities are no longer built ‘for eternity’ like Rome, not even for
centuries, and even landmark protection centers in many places on just a few prewar
legacies. Most other urban structures existing today may be expected to have a
useful life cycle of 50 to 100 years, trending downward. Rising price levels
for land in highly developed central locations and the stunning opportunity
costs of suboptimal use dictate a timely replacement of unproductive real
estate in the wake of new technologies, but also to accommodate synergies
created by nearby developments or improved transportation infrastructure. Yet,
at the same time, only a rapidly dwindling percentage of the debris left by
demolition finds its way to out-of-town landfills, and that signals hope: in
some environmentally conscious and well-administered cities around the globe,
at least half but potentially a lot more of demolition waste can be recycled
and finds recurring use in new construction and industrial production. This diagnosis
represents a material value of at least six but often seven or even eight figures
– per demolished object. With more than half the planet’s population already dwelling
in urban habitats, these dimensions are motivation enough to refer to the
recovery of such percentages of the ‘gross demolition product’ as ‘urban
mining’ and to redefine
‘waste’ as an increasingly precious asset.
So
it is appropriate to look at urban real estate as a kind of warehouse of raw
materials, containing sand, gravel, concrete, metals, woods and synthetics –
all commodities in limited supply. Yes, even wood can be recycled, it happens right
here in the U.S., and even for upscale uses such as custom furniture. To carry a ton of concrete
to a waste dump may run a tab between $15 and $30 while the same ton may be
sold as recycled material for up to $8. Also because of increased public awareness
and vocal opposition to environmental toxicity, there is increasing scarcity of
landfill acreage in the proximity of major urban settlements. An even more
valuable sector of urban debris is e-waste,
usually shipped to places like China or India but also to all of West Africa,
particularly Liberia, Ghana, Cote d’Ivoire, Benin, Nigeria. Metal deposits in
e-waste are up to 40 to 50
times richer in target elements than ore extracted from mines. The novel
science of hydrometallurgy
now provides advanced technologies for refining pure metal fractions out of
mixed raw material resources in relatively simple processes, safely and at
comparatively very low cost.
Take
urban
copper, for example. It is an amazing resource to tap into: an Austrian
study showed that electrical household
appliances contain 6.4 percent of copper used in the country, cars account for
8.7 percent, but real estate takes up 84 percent of “urban copper.” On average, today’s buildings house seven
times more metal as buildings contained a century ago. About half of naturally occurring copper has
already been used up in our existing urban structures. Given the speed of urban
development, it does not take a mathematician to predict a time when the market
price of copper might qualify it as a ‘precious metal.’ Despite recent
findings on the Pacific Seabed limiting
global dependency on deposits in China, recycling
rare earth elements
will remain a vital necessity at least
until they are obviated by technological innovation. The U.N. Environmental Program estimates that 50
million tons of e-waste are generated annually around the world – a rapidly
rising tide. Their StEP initiative (Solving
the E-waste Problem) found that the global production of electronic items
used 320 tons of gold and more than 7,500 tons of silver annually, amounting to
an aggregate
value of $21 billion - of which just 15 percent is currently being
recycled. Urban mining is arguably the most highly yielding alternative source available
to us to
reduce reliance on metal imports.
Which
begs the question of its practicalities and of forward-looking facilitation.
Building
Information Modeling (BIM) is a new planning
tool that contains three-dimensional
virtual CAD modeling of construction projects from a first sketchy draft to
detailed plans to a call for proposals to site inspection to facility
management. A
unified standard for BIM is expected to be enacted by the European Union by the
end of 2015. Singapore
has already introduced BIM as a requirement in all plan submissions for
projects with gross floor area exceeding 5000 square meters.
No
different in a sense than treasure
maps of old, only a lot more accurate and reliable, BIM’s importance for urban mining
is difficult to overestimate: it can considerably reduce the cost of efficient
waste separation. When networked, it is also a potential source for data feeds
needed to create a register of “mineable” materials integrated in any existing
structure built with BIM. Today, every
demolition object has to be evaluated individually – often based on almost
unsubstantiated estimates. This relates to the potential of BIM technology like
an abacus does to a modern computational device: BIM can provide almost every
level of detail required (or justifiable in terms of cost). It is the
contracting industry’s functional equivalent of grocer’s “farm-to-fork” databases
and increasingly detailed mandated accounting
for every step the product takes to its final consumer.
Material
recycling also significantly reduces a demolition’s CO2 footprint. For example,
recycled concrete consumes substantially less gray energy than the
production of primary concrete. Additionally, about two thirds of trucking runs
to landfills sites may be saved. An
almost trivial cliché says that one man’s trash may be another man’s treasure,
but the first part of that equation is no longer sustainable in urban
environments expected to house twice the current human population by the end of
the 21st century. Turning every increasingly networked and recorded ‘smart
city’ into a proverbial perpetuum mobile
by tightly integrated, institutionalized urban
mining is not only a potential given available data and technology but a
vital necessity.