CO2 Capture

What is an LCIA?

life cycle impact assessment, looks at impacts on different environmental focus areas after compiling results from LCI

what is system expansion?

expands the LCA system boundary to include additional functions/products, so the compared systems provide the same functions, best for large systems

ex: CHP plant producing electricity + heat —> compare to system producing the same electricity and heat separately

what is substitution?

gives a credit for an avoided product/process because a co-product replaces it in the market

ex: heat from a CHP plant replaces heat from a gas boiler —> substract the environmental impacts of the avoided gas heat

What are the foreground, background, and unit process in an LCA?

foreground = production process itself

background = inputs from industry, energy, transport, materials, waste services

unit process=one small process in the foreground whose inputs and output can be clearly identified

what is included in LCI data?

products and byproducts, demand/input for resources, materials, energy, and water, waste generation and disposal, direct emissions, transportation

what do we have to weight LCIA results by?

GWP over 100 years

how can we adjust LCIA results to better understand the relative results of each indicator?

normalization and weighting/aggregation

what is SWOT in a LCA? what does each part refer to?

SWOT = strengths, weaknesses, opportunities, and threats and examines the LCA itselff

strengths = quantification and evaluation of emissions

weaknesses = how robust and reliable for new tech or complex systems

opportunities = momentum of LCA and integration into other analysis

threats = abuse, skepticism, and narrowly-focused LCAs

What are the different ways hydrogen can be produced with CCS?

electrolysis, natural gas reforming, coal gasification

what is important for an LCA of hydrogen from electrolysis?

GHG intensity of electricity input

what is important for an LCA of hydrogen from natural gas reforming with CCS?

capture rates of CO2 and methane emissions during supply chain

What is the least carbon intensive way to generate hydrogen?

green hydrogen via electrolysis from renewables or biomass with CCS

how does biomass source impact LCA of hydrogen production?

must be sustainably sourced for negative emissions to occur, not always available

can fossil power with CCS qualify as a low carbon electricity source?

yes, if substantial GHG reduction occurs over entire life-cycle (80-90%)

drawbacks of CCS in terms of LCA?

increases electricity input (but GHG intensity still decreases)

why are H2 fuels needed in energy transition?

replacement of intensive fuels with hard to abate emissions, trading, seasonal supply and storage

what are shortcoming of H2 fuels?

energy intensive, climate impact is highly process dependent, high CO2 abatement costs, availability

how much more electricity do e-fuel pathways require compared to direct electrification?

2-14 times

Why do H2 fuels have high CO2 abatement costs?

high CO2 prices required—>high e-fuel costs, not economically competitive yet

what sectors are best for H2 fuel use?

aviation, maritime shipping, chemical industry, high temp heat

what are the benefits of slow pyrolysis for biochar?

needs lower temperature so less energy intensive

what is the carbon stability factor and what does it depend on?

fraction of carbon in biochar stored in the soil for 100+ years, depends on pyrolysis temp and soil temp

most stable for low soil temp and high pyrolysis temp

what qualities provide the best biochar stability and yield

high pyrolysis temp, low soil temp, high lignin content, low moisture, low ash content

what does biochar climate impact depend on the most?

carbon removal and type of substituted heat and electricity

when is DACCS negative?

if heat and electricity supply are low carbon

when is biochar CO2 neutral or negative?

stable carbon, sustainable biomass feedstock

how do we decide what price to set the carbon tax at?

want it high enough so that polluters internalize the costs, but not so high that the economy is burdened

set tax higher than the abatement costs of CO2 such that polluters are inclined to invest in CCS

what’s the difference between a carbon tax and carbon credits?

tax = setting the price, credits = setting the cap

what is the recommended carbon price as compared to the current price?

current = around 60-70 usd/ton

recommended for 2C target: 63-127 usd/ton

recommended for 1.5C target: 226-385 usd/ton

carbon price should be flexible to follow market

what is a learning curve?

specific costs per ton vs cumulative installed capacity, slope = learning rate

how fast costs decrease as installed capacity increases

what is an experience rate?

specific cost reduction per doubling of cumulative output

what is the experience rate of DACCS?

12-13%

what are elements of the Swiss climate strategy?

net-zero by 2050, waste incineration with CCS, cement and chemical plants with CCS, NETs with some storage in switzerland, RE

what does the swiss climate and innovation law focus on?

reducing avoidable emissions, balancing hard to abate emissions with CDR

what are switzerlands hard to abate emissions? how will they be tackled?

industry and fossil waste (7Mt)—> point source capture plus NETs

agriculture (5Mt) —> CDR via DAC/NETs abroad

what is switzerlands plan for tackling aviation emissions?

70-100% subsitution of fossil fuels with SAF to offset 1-2Mt from aviation

what is the CO2 act?

CO2 levy on fossil thermal fuels for heating —> 120 chf/ton —> plans to increase to 210chf/ton

heating fuels and imported motor fuels are taxed and money is used for sustainable building programs and redistributed to population and economy —> % of emissions offset —> plans to increase percentage

defines a cap and trade system similar to the ETS —> 100 chf/ton CO2

tax on plane tickets —>no current price but plans to establish 30-120 chf/ticket

list the phase and pressures used for different CCS transport?

iso-containers on trucks: liquid at medium pressure (16 bar)

ships: liquid at low or medium pressure (8/16 bar)

pipelines: gas at medium pressure (10-30bar) or liquid at high pressure (80-350 bar)

types of CCS in development in CH?

neustark storing CO2 in concrete, storage in saline aquifers with other injection pilots

cost of CCS in CH?

180 chf/ton CO2, capture and domestic transport are most of the cost

how do emission goals vary for different swiss sectors?

CH overal: net zero by 2050

companies: net zero scope 1 and 2 by 2050 (scope 3 recommended)

administration: net zero scope 1, 2, and 3 by 2040

what is CBAM?

climate border adjustment mechanism

what sectors have thee largest potential for point source CO2 capture?

waste treatment, cement, biomass and biofuel, refineries, steel, natural gas

what are the european commission’s goals for capture and storage by 2030 and 2040?

2030 = 50 Mt/y

2040 = 200 Mt/y

what is the longship project?

CO2 cpatured from cement factor and waste-to-energy plants in norway to be taken to northern lights hub

what is project greensand?

CO2 storage in a geological reservoir off the Danish coast, with emissions come from biomethane production

what volume of CO2 can each transport method transport?

iso-containers: 20t

trucks: 26-50t

river-based ships: 3000-5000t

ocean-based ships: 5000-50000t

how does pressure of transported CO2 affect energy requirement?

lower transport pressures require more energy and higher costs lower temps are required to keep CO2 in liquid phase, and cooling is costly

what are considerations for high-pressure CO2 transport?

more cost-effective but requires high material input because tank walls must be thicker

compare ship CO2 transport at 8 and 16 bar

8 bar: low pressure

-high density at low temp (-49C)

-scalable tank and ship sizes

-close to solid phase, lots of cooling and complex insulation

16 bar: medium pressure

-slightly higher temp (-28C) so less cooling needed

-only at small scale thus far

-technically challenging and requires more steel for tank

what is the cost per ton of CO2 transported inland?

1 EUR/t CO2 per 10 km

what transport options are best for what distances?

long distance: pipelines or offshore ship

medium to short distance: barges

close by on land: truck

what critieria do we use to select CO2 transport mode?

economies of scale (cost reductions for increased volumes), greenfield infrastructure, time horizon, seasonal fluctuations, conditioning requirements, GWP, holding time, duration variability

what is holding time?

time period where CO2 can be transported before leak or pressure release occurs

trade-offs off transport modes?

truck and train are readily available and cheap but take long periods of time

barges and ships are much quicker but costly and with high seasonal fluctuations

what is ACCSESS?

providing access to cost-efficient, replicable, safe, and flexible CCS

test CO2 capture and use for integration in industry, develop and improve CCS chains, engage and inform stakeholders

how much CO2 should CH export each year by 2050 and how costly would it be?

7 Mt, 16.3 billion CHF

why is a CO2 pipeline network in CH difficult?

varying terrain, space limitations, electricity demand, and infrastructure requirements

how much subsurface storage potential does CH have?

52 Mt CO2

Yearly GHG emissions and CO2 emissions from world and switzerland?

world: about 40 Gt CO2/year

switzerland: about 34 Mt CO2/year

largest emitting economic sectors?

electricity and heat production, agriculture, buildings, industry, transportation

ETH sustainability strategy?

eliminate 50% of scope 1 and 2 by 2030, and 20% of scope 3

become net zero by 2040 for scope 1 and 2, and next zero for scope 3 by 2050

How does petroleum and NG form?

tiny marine organisms die and sink to ocean floor, are buried at high temps and pressures until organic matter transforms into oil and gas within the source rock and accumulates in geological traps

Natural gas basic chem?

mainly methane, has high energy content by mass, and low CO2 to energy content (less emissions)

often contains impurities like CO2 and H2S that are removed via gas sweetening

oil basic chem?

hydrocarbons, must be refined once extracted (usually in a distillation tower)

how does coal form?

incomplete decay of terrestrial plants (peatification) and burial

coal chemistry?

highest carbon content and contains lots of organic matter and impurities, highest CO2-to-energy content (lots of emissions)

hydrogen deficient with high levels of aromatics and organic oxygen

what does C/H ratio indicate?

lower C/H ratio means less CO2 emissions upon burning (aka we want more hydrogen and less carbon, like with methane)

indicates carbon content

what reduces the heating value and increases CO2-to-energy ratio in fuels?

water and various noncombustible elements

what is heat content in a fuel determined by?

amount of carbon and hydrogen since heat is produces when C and H combine with O during combustion

what are some biomass sources?

wood chips and pellets, lumber, sawdust, agricultural crops, paper, cotton, yard waste, animal manure or human sewage

where do the CO2 emissions in cement and steel production come from?

cement: part from material inputs/feedstock, part from combustion of fuels

sttel: almost all from fuel combustion

how is biomass converted into a fuel and what fuel phase does each process produce?

direct combustion = heat

chem conversion = liq fuel

biological = liq and gas fuels

thermochhemical = solid, liq, andd gas fuels

how do CO2-based fuels work?

direct utilization, hydrogenation, or incorporation

high energy catalysts are reactedd with CO2 to form CO2-based products (larger energy need)

CO2 can be used as C source in production of synthetic fuels

can be extracted directly from air and split with water ans sunlight through redox rxns to yield syngas (CO and H2)

syngas can be processed into other fuels

list the 6 types of NETs and describe

afforestation: plant tress where there haven’t been any for at least 50 years

soil carbon management, including biochar: sustainably manage soils to retain more carbon, introduce biochar to the soil, reduce tilling (which frees humus, a carbon-rich material, from the soil)

BECCS: energy from biomass with CCS

DACCS: direct air capture and sequestration

enhanced weathering: crushed minerals bind CO2 chemically and then can be stored

ocean fertilization: iron or other nutrients added to ocean to increase absorption of CO2 by algae

describe post-combustion capture, benefits and limits, and energy requirements

capture CO2 from fuel after burning in air, separate CO2 and N2 after removing particulates from flue gas

can be retrofitted, relatively mature technology, most of energy to heat for reboiler and electricity for compression

ex: amine scrubbing, CAP

describe oxy-combustion capture, benefits and limits, and energy requirements

use an ASU to separate N2 from air, then burn fuel in pure O2, capturing CO2 after combustion after separating from H2O

hard to retrofit, has only been used with coal thus far (no NG), expensive and complicated

most of energy is from electricity for ASU and compression

ex: linde process, FGR, PSA

describe pre-combustion capture, benefits and limits, and energy requirements

put fuel into a gasifier to separate the CO2 and H2 before combustion, do a water gas shift, then run turbines on H2 fuel, capturing N2 and water at the end

can’t retrofit, not very available yet, heat for reboiler and electricity for compression

ex: IGCC, steam methane reforming, PSA

describe pros/cons of post-combustion capture for a cement plant

industrial process remains unchanged (retrofit), minimal downtime for CCS addition, unchanged cement product quality

most energy demand in form of heat but can integrate heat with plant

describe pros/cons of oxy-combustion capture for a cement plant

retrofit is difficult to impossible, cement quality maintained, energy demand mostly in form of electricity but power gen from excess heat is possible

how can CO2 compression be made more efficient?

intercooling to reduce the temperature lift across a compressor stage by removing heat between steps, reducing the work needed

how many emissions can we emit until 2100 if we want to stay on 1.5C target?

500 Gt CO2 (already emit 40Gt per year)

what is the basis for the 2C target?

how much risk and damage to existing systems we are willing to accept, predictions for future emissions and energy consumption, societal challenges, technological lock-in

What models make up overall emissions calculations?

radiative transfer model, climate model, and carbon cycle model

describe the radiative transfer model. what is it’s key parameter?

radiative forcing = R = W/m²

how additional radiation retained by earth affects heating and temperature rise, includes affects from albedo, aerosols in atmosphere, heat sinks, and GHG warming

absorption of longwave radiation by GHG and re-radiation back to the surface

externally imposed perturbation in radiative energy budget

what range of the light spectrum is incoming solar radiation and what part of range is absorbed longwave radiation?

incoming = UV (shortwave), absorbed = IR (longwave)

describe the climate model. what is it’s key parameter?

transient climate response = gamma = increase in temperature for doubling of CO2 concentrations above 1850 levels (280 ppm)

looks at how atmospheric temps change as CO2 emissions in the atmosphere increase (weakly sensitive or strongly sensitive climate response)

describe the carbon cycle model. what is it’s key parameter?

airborne fraction = f = 1- f_land - f_ocean —> about 46% for air

how much CO2 ends up in atmosphere after accounting for carbon sinks

looks at how cumulative emissions relate to actual CO2 atmospheric concentrations, and categorizes weak and strong sinks

what should climate models consider?

conservation of momentum, energy fluxes and mass, discretization

what are the representative concentration pathways?

describe how different levels of emissions in the future would affect radiative forcing and hence temp rise, smaller R number means lower radiative forcing

how fast are atmospheric concentrations of CO2 increasing?

2 ppm per year (2% yearly increase in FF emissions)

what is the difference between CDR and CCS?

CDR = process that draws down carbon from the atmosphere and stores it durably long-term

CCS = capturing emissions from point sources to avoid atmospheric pollution, and storing

how does CO2 concentration in a gas affect energy demand for capture?

there’s a minimum work to separate components, so more concentrated is more energy efficient

what is the difference between CO2 captured and CO2 avoided?

captured > avoided

always some enegry requirement for the CCS itself so overall emissions with CCS will be greater before capture

avoided = captured - extra = original emissions = new emissions

describe absorption, cryogenic, membrane, adsorption, and chemical looping separation

absorption: happens in bulk solvent

cryogenic: low temp distillation makes use of different material boiling points

membrane: physical and chemical interactions with membrane

adsorption: attaches to the surface of a solvent, via Van der Waals forces or bonding

chemical looping: uses metal cations to separate out components

when is physical ad/absorption favored to chemical?

for high pressures and high CO2 concentrations

describe amine scrubbing and characterize it

dissolve CO2 in amine solvent, heat in reboiler to regenerate the amine, do a water-vapor strip, where CO2 and water are evaporated from the amine solution, then water vapor is condensed, leaving us with a pure CO2 gas

chemical absorption

describe how an absorber column works

uses tight packing of filters and membranes to increase interfacial area for liq and vapor phase to react

height of column determines capture rate, diameter determines gas flow rate

why are amines used for scrubbing?

highly selective for CO2, low volatility (stay in solution), low viscosity so not too think

absorption chemistry

what are the risks of amine degradation and how can it be controlled?

amine can reaction to form toxic NOx byproducts, which are carcinogenic

control degradation thru flue gas pre-treatment, solvent reclaiming, flue gas wash