1 Materials & Resources Sankey Diagrams Scott Matthews /

Administrative Issues  HW 4 Due Today  No HW due next week (taking a week off)  Project Updates  Any left?  HW 5 coming  Start tracking your expenses AND your general “material/resource” flow starting tomorrow am. Will need to for next HW. 2

Mass Balance  Fundamental principle of engineering / environmental engineering (law of conservation of mass)  Commoner: “everything must go somewhere”  Physical quantities  Energy  Calories, etc.  Relevant: stocks and flows, ins and outs 3

Basic Plan for an MFA  Begin building a simple IN=OUT model  Start assembling IN, OUT flow data  Are there many more relevant IN, OUT flows?  Is there a substantial stock or sink?  Do we have sufficient data to quantify them?  Continue iterating as data and time allow  When done, summarize as many disaggregate stocks and flows as possible  Typically express results “over life cycle” 4

5 Source: USGS, Obsolete Computers, “Gold Mine,” or High-Tech Trash? Resource Recovery from Recycling

Our Computer “MFA” 6

Study 1997 Study

Computer Flow Study Results  1991 Model:  By million sold, 150 million landfilled  1997 Model:  By 2005 – 680 million sold, 55 million landfilled (one acre piled 4000 feet high)  150 million recycled (originally almost none)  What affects them? Shouldn’t percents/etc change year by year (ie by an increasing or decreasing trend of % recycled?) 8

Policy Relevance of MFA  Can we track natural versus anthropogenic flows?  JIE paper – Cadmium – only way to reduce is to eliminate inflow  But inflow is byproduct of Zinc; either need to eliminate zinc production or cut off co-product  Structure of such studies – and construction of the stock/flow models – yields insights  Can we learn more about connections between stocks and flows, our activities? 9

MFA Issues  Data / methods are largest barriers (conceptually simple otherwise)  What about uncertainty? 10

Sankey Diagrams  Generally used for Energy flow analyses  Implicit assumptions  The diagrams concern quantity sizes that are related to a period in time or to a functional unit, such as a product unit.  The quantity scale is proportional (i.e., twice the quantity is represented by an arrow that is twice as wide).  Inventories are not taken into account (i.e., there is no stock formation).  An energy or mass balance is maintained. 11

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13 Source: WRI,

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Lead Flows 1970 (USGS) 15

Lead Flows

Non-renewable resource consumption  As new resources identified, production and consumption small, grow slowly  With new uses, new demand, thus exploration  Demand continues as we find new supply  New supplies become harder to find  Inevitably raises costs, reduces demand  Feedback loop to looking for less supply  Eventually “known” reserves run out 17

Hubbert’s Curve (Shell Oil 1950s)  Projects rate of oil production over time  Based on peak of oil well discovery in 1948, Hubbert in 1956 accurately predicted that oil production in the contiguous United States would peak around  Since applied to global oil production  Implication: a steep drop in production implies global oil production will decline so rapidly we will not have enough time to develop alternatives 18 Source: (original 1956 report)

Hubbert’s assumptions  Production curve:  We know production=0 at t=0, t=infinity  If P=dQ/dt (change in production)..  Area under curve = total production  Q(t) cumulative production  Hubbert inevitably assumes symmetric production functions 19

20 Source

Hubbert’s “prior data”  Production in “old” regions of the US 21

 Any curve that starts and ends at zero, hits a peak, and has as the area the total available resource is possible  The question is which is more likely? 22

In-Class Exercise: Hubbert curve for global oil (conventional only)  Find/draw a Hubbert curve.  Simply put, relevant data to estimate ultimate production are:  U= cumulative production, reserves, “yet to find”  “Yet to find” a “round off error” kind of number representing oil we think is out there  Sum of these 3 ~ ultimate production (U)  Saudi Arabia - #1 producer - notoriously quiet on publicly revealing their amount of reserves. Why? 23

Data Point #1 24

Data Points #2 25

Relevance for Other Materials  Fossil fuels, e.g. petroleum are primary needs in production of everything else  Plastics – petrochemical feedstocks (part of push for biobased feedstocks) 26