LCA Midterm

purposes of LCA?

• support broad environmental assessments

• establish baseline info for a process

• public policy

• guide product + process dev

functional unit (def + requirements)

• the basis on which a system is evaluated in an LCA

• Requirements:

  • precise + measureable

  • captures the service performed + compares products or systems on the basis of equiv service

True / False: system boundaries have to include all life cycle stages for a comprehensive LCA

False - only includes selected processes; does not have to include all stages, but must support the goal statement

Foreground processes

are specific to the system under study and may be under the control of the analyst or the analyst’s organization

background processes

are more generic and will exist without the system of study

• good example is electricity production

cradle-to-grave vs. cradle-to-grate

“to-grave” include end of life operations

“to gate” cut off before use + end of life

• product is sitting in the factory ready to go out T

True / False: cradle-to-gate LCAs include transportation and distribution, but not use + end of life

False - ends after processing / before transportation + dist

primary energy

energy content of fuels found in nature

secondary energy

converted forms of primary energy

is crude oil primary / secondary energy?

crude oil = primary

• converted to gasoline (secondary energy) for use

coal is primary or secondary E?

primary

purchased energy

the amt of electricity/natural gas on the bill; commercial buildings + facilities have this

full fuel cycle energy

the full amount of energy required to get purchased energy to the point of use

• considers extraction, processing, transportation etc

purchased energy + all energy from earlier steps

what type of E is electricity (primary / secondary) ?

secondary

what type of E is steam (primary / secondary) ?

secondary

what type of E is tidal energy (primary / secondary) ?

primary (ocean tides)

what’s the diff between lower heating value (LHV) and higher heating value (HHV)?

LHV excludes latent heat of vaporization of water

How can you measure methane leakage for an LCA / what is the diff between these two approaches?

bottom-up: isolate + measure emissions from diff equipment

top-down: fly over emissions measurements with helicopters

What are some top-down ways to measure methane emissions ?

satellites

aircrafts

drones

What are some bottom-up ways to measure methane emissions ?

wheeled vehicles

handheld tools

Nationally, we get electricity naturally from which source the most?

natural gas

What is the general formula used to calculate the energy needed to produce a product?

mf = mass of functional unit [ kg ]

mi = mas flow, i [ kg ]

ei = energy flow [ MJ ]

Ki = full fuel cycle value of the impact category of interest per unit mass or energy of i [ MJ / kg or MJ / MJe]

What is the impact vector used to calculate the energy needed to produce a product?

what are some primary sources of data?

• national emissions inventory

• toxics release inventory

• USDA stats center

What is a Monte Carlo?

a sampling approach which determines the effect of input uncertainties on the output

What is a data quality matrix?

A tool used to quantify the quality of data in an LCA

• evaluates points across 5 key indicators on a score of 1-5

What are the 5 indicators on a data quality matrix?

1. reliability

2. completeness

3. temporal correlation

4. geographical correlation

5. technological correlation

True / False: “completeness” on the data quality matrix reviews how old the data is compared to your study year

False - that is temporal correlation

true / false: “reliability” on the data quality matrix reviews if the data is based on estimates or actual measurements

true

How does a Monte Carlo work? (4 main steps)

1. each input has its own probability distrubution

2. random values are sampled from each distribution

3. output data is simulated for each sampled imput

   1. this would be the impact factor like energy of GHGs

4. based on the distribution of outputs, we can calculate a confidence interval for the results

What does allocation mean ?

divide the input burdens and output burdens among the different co-products so that each co-product has its unique LCA.

Energy allocation

considers energy content of co-products

What are some examples of energy allocation?

• petroleum refineries produce energy products valued for their energy content

  • power plants may produce steam alongside electricity

mass allocation

allocates burdens based on mass share

What is a “burden” in terms of co-product handling ?

• resource consumption: energy, water

• emissions: greenhouse gas, water pollutants, etc

when can market value allocation / economic be used?

• when a plant or facility would shift its slate of co-products depending on market factors

• when a process exists because it produces a very high market value product. Co-products come along for the ride

Allocation governing equation

unallocated flow * allocation factor = allocated flow

system expansion (displacement)

give the main product credit for co-products displacing existing products

what’s the difference between allocation and displacement?

• allocation : divides the environmental “blame” among co-products based on a specific physical or economic factor

• displacement: gives the main product a “credit” for avoiding the production of the co-product elsewhere

System-level allocation

A "Black Box" approach where burdens are divided based on the final outputs of the entire facility.

• You draw one large boundary around the whole plant. You take the total inputs (energy, water) and total emissions, then split them among the co-products using a single factor (like total mass or total market value)

process-level allocation

A "Pay-for-What-You-Use" approach that assigns burdens step-by-step to specific unit operations.

• you break the plant down into individual sub-processes (e.g., Cooking, Fermentation, Distillation).

True / False: your displaced burdens should sum to total burdens

false - allocated burdens should sum to total burdens

• false for displacement because you are giving “credits” based on other systems outside the factory

Pros & Cons of Allocation

pros:

• simple

  • always sums to 100% of total impact

• data availability - only need inputs + outputs of own process

• stability - results don’t change based on other facilities

Cons:

• arbitrary slicing

  • ignores how co-product may be helping the environment

Pros & Cons of Displacement

Pros:

• ISO preferred bc it models actual consequences

• rewards product for efficiency

• policy advantage - can result in much lower (even negative) carbon intensity scores

Cons:

• high data burdem = need lots of accurate data on other processes

• more mathematically complex than allocation

What is the formula for Global Warming Characterization?

What website can you use to track human health / toxicity of substances?

TRACI

Ecotoxicity units in TRACI

CTU per kg

What is CTU

comparitive toxicity units

what does CTU estimate?

the increase in morbidity in the total human population per mass of a chemical unit emitted

what substance has the highest ecotoxicity score?

Why would u pick mass / energy / market value allocation over the others?

• mass: system produces products sold based on quantity

• energy: produces products used as energy carriers (i.e. electricity, gas, fuel)

• market value: products vary in the value and system may exist because one of the co-products has a very high market value