Canada Becomes a Leader in Carbon Capture

Canada Becomes a Leader in Carbon Capture

By Karlee Bamford, Treasurer for the GCI

The attention of international media has been captured by the remarkable success in CO2 sequestration achieved by the Canadian company Carbon Engineering, located in Squamish, British Columbia. Sustainability-related, world-saving initiatives often have an easier sell in the media than, say, incremental advances reported by researchers on equally sustainable academic pursuits (rough, eh?). In this instance the craze over Carbon Engineering’s advances has been amplified by the news of their recent partnerships with household-name energy and oil giants, such as Chevron, BHP, and Occidental Petroleum, in the form of a CAD $68 million investment.  So, what is this incredible advance?

From the success of their pilot plant and the data they’ve accumulated thus far, Carbon Engineering implementation of their technology has achieved capture of The technology in question can be split into two major advances. Referred to as direct air capture, or DAC, the first process developed by Carbon Engineering involves the transfer of gaseous CO2 from ambient air to an absorber fluid, a strongly basic solution of sodium or potassium hydroxide. The transfer process is achieved using an air-liquid contactor, designed and described by the company in 2012,4 that involves an array of fans, pumps, cheap PVC piping and structure, and fluid distributors. These components are fundamentally no different than those commonly found in cooling towers used as heat exchangers for water cooling. However, the orthogonal geometry (Figure 1) of air (atmospheric, ~ 400 ppm CO2) and fluid (the absorber) flow differs significantly, making repurposing of existing cooling tower designs for DAC an inefficient and expensive strategy for CO2 capture.

Picture

Figure 1. Commercial realization of air-fluid contactor designed by Carbon Engineering. M = Na or K. Image obtained from CanTech Letter and modified.5

The CO2 taken up by the alkaline absorber fluid is converted to carbonate (CO32-) salts and can be precipitated from the aqueous solution by treatment with calcium hydroxide to give calcium carbonate pellets. The captured CO2 can thus be stored as calcium carbonate or can be cleanly regenerated as pure CO2 gas, with elimination of a CaO , at high temperatures (650 °C) for commercial resale. The byproduct CaO may even repurposed by conversion back to Ca(OH)2 in a lime slaker, using water.1 Carbon Engineering has been piloting this process at their facility in Squamish since 2015, according to their website, after having tested a smaller prototype from 2010 and published the performance results in 2013.6 At the time of Carbon Engineering’s founding and until as recently as 2018, no commercial-scale air capture systems had been developed, which was a direct result of the anticipated inefficiency of CO2 capture using conventional cooling tower designs.4 Undeterred, Carbon Engineering has proven otherwise with their innovative use of cross-flow geometry.

The second break-through technology from Carbon Engineering is their patented Air To FuelsTM process, which they’ve been piloting since 2017. Taking the stored CO2 from their DAC process, Carbon Engineering has successfully produced a clean, sulfur-free, source of hydrocarbon fuel that requires no further modification for consumer consumption. The process involves passing the regenerated CO2 gas through a reactor containing hydrogen (H2) gas to generate synthesis gas (syn-gas), a mixture of CO and . The syn-gas is then passed through a Fischer-Tropsch reactor where the synthetic hydrocarbon fuel is thermally generated over a heterogenous base-metal catalyst (e.g. iron, cobalt, nickel).7

The technologies have been developed by the research groups of founder and U of T alumnus Prof. David Keith. Prof. Keith is currently faculty at Harvard University in the School of Engineering and Applied Sciences. To date, the company has filed 13 patents and produced numerous publications describing their innovations. According to media reports,8 recent multimillion-dollar investments will allow their and the company has already signed a memorandum of understanding with Squamish First Nations about their intentions.9

One of the most attractive aspects of the DAC and Air to FuelsTM technology is location. Plants could, hypothetically, be built anywhere, as CO2 is well mixed in the atmosphere and Carbon Engineering’s technology does not require that CO2 capture occur at the point of CO2 generation as in, for example, CO2-scrubbers used in exhaust systems.

However, with the excitement surrounding Carbon Engineering’s projected ability to capture CO2 at low cost and high volume, controversy has inevitably been close to follow. The interest from large oil corporations in this technology may not be as principled in sustainability as it appears but driven in part by their need for large volumes of CO2 for so-called green fracking (hydraulic fracturing). Supporting further oil extraction in this way goes completely counter to the need for elimination of emissions that the 2018 Intergovernmental Panel on Climate Change (IPCC) report clearly indicates must accompany advances in carbon capture and storage.10 Still, perhaps the positives outweigh the negatives in this instance. This very week, Environment and Climate Change Canada reported that Canada is warming at twice the rate of the rest of the globe.11 The need for efficient technologies to address climate change has never been more immediate. Fortunately, Carbon Engineering is not alone: at least two other companies with commercial plans for CO2 capture have started in Switzerland (Climeworks)12 and the USA (Global Thermostat).13 Whether the Canadian solution is adapted worldwide will depend not only upon Carbon Engineering, but also upon how these alternative approaches evolve.  For once, it is probably best not to pick a team to cheer for but, instead, hope that each country’s company develop a complimentary capture strategy to address the international dilemma that is climate change.

References:

  1. Keith, D. W.; Holmes, G.; St. Angelo, D.; Heidel, K., Joule 2018, 2, 1573-1594.
  2. American Physical Society. Direct Air Capture of CO2 with Chemicals: A Technology Assessment for the APS Panel on Public Affairs. June 1, 2011 https://www.aps.org/policy/reports/assessments/upload/dac2011.pdf ; accessed April 24, 2019.
  3. Carbon Engineering, https://carbonengineering.com/ .
  4. Holmes, G.; Keith, D. W., Trans. R. Soc. A 2012, 370, 4380-403.
  5. Artist’s rendition of a commercial scale Carbon Engineering contactor, CanTech Letter. https://www.cantechletter.com/2016/10/squamish-b-c-s-carbon-engineering-begins-scale-co2-capture-new-deal/ ; accessed April 4, 2019.
  6. Holmes, K. Nold, T. Walsh, K. Heidel, M. A. Henderson, J. Ritchie, P. Klavins, A. Singh and D. W. Keith, Energy Procedia, 2013, 37, 6079-6095.
  7. Heidel, Keton et al. Method and system for synthesizing fuel from dilute carbon dioxide source. WO2018112654A1, 2017.
  8. BBC News, Matt McGrath. Climate change: ‘Magic bullet’ carbon solution takes big step. April 3, 2019 https://www.bbc.com/news/science-environment-47638586 ; accesed April 3, 2019.
  9. CBC News, Angela Sterritt. In fight to combat climate change, Squamish Nation joins forces to capture carbon. November 29, 2018. https://www.cbc.ca/news/canada/british-columbia/in-fight-to-combat-climate-change-squamish-nation-joins-forces-to-capture-carbon-1.4924017 ; accesesd April 4, 2019.
  10. Intergovernmental Panel on Climate Change 2018 Summary for Policy Makers, Global Warming of 1.5 °C. https://www.ipcc.ch/site/assets/uploads/sites/2/2018/07/SR15_SPM_version_stand_alone_LR.pdf ; accessed April 4, 2019.
  11. Environment and Climate Change Canada, Canada’s Changing Climate Report, April 1, 2019. https://www.nrcan.gc.ca/environment/impacts-adaptation/21177 ; accesed April 4, 2019.
  12. Climeworks, http://www.climeworks.com/
  13. Global Thermostat, https://globalthermostat.com/
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The plastic problem – accumulation before alternatives

The plastic problem – accumulation before alternatives

By Karlee Bamford, Treasurer for the GCI

Plastics undoubtedly play a central role in our daily lives and played a pivotal role in the development of consumer societies across the globe for over a century. Concurrent with newfound materials and newfound possibilities, unprecedented environmental problems have emerged as a result of our reliance on plastics. The accumulation of plastics in allocated disposal sites (e.g. landfills) and in otherwise uninhabited spaces (e.g. beaches, open ocean) present threats to human health, water security, and food supply. These challenges now impact communities globally, irrespective of their actual contribution to the generation of plastic waste, and affect individuals of all economic backgrounds.

Figure 1. Examples of waste plastic accumulation in landfills and the environment. Images source: Pixabay.

Given the scale and significance of these challenges, is there anything that chemists can do to resolve this panhuman problem? A recent blog post from the Green Chemistry Initiative (https://greenchemuoft.wordpress.com/category/author/molly-sung/) highlighted the advances that have been made in synthetic and materials chemistry towards plant-derived and biodegradable plastics as alternatives to traditional petroleum-derived plastics. While this is undoubtedly a crucial area of research as humanity has become permanently dependent on plastics, the design of next generation plastics that are inherently sustainable will not mitigate the overwhelming impacts of existing plastic waste. Arguably, attenuating the problem of plastic waste is more important than finding alternatives to traditional plastics. Indeed, the decomposition time for products made from the top four families of commodity plastics (PP, PE, PVC, PET), produced on a 224.6 million tonne-scale alone in 2017,1 is estimated at 1 to 600 years in marine environments2 and considerably longer in landfills due to lack of moisture.4

Figure 2. Examples of the top five most-produced commodity polymers and their production scale in 2017.1,3

Traditional plastic-recycling methods are not equipped to resolve the issue of waste plastic accumulation either. Recycling can be broken down into three distinct varieties: primary, secondary, and tertiary.5 Primary recycling, which is equivalent to repurposing or reusing, is used limitedly for products such as plastic bottles, typically made of PET, which be directly reused following the necessary sterilization. Secondary recycling involves mechanical processing of plastics into new materials and frequently results in reduction of the plastics overall quality or durability due to the thermal or chemical processes involved. Primary and secondary recycling account for the majority of recycling efforts, however, as a consequence of poor consumer compliance (e.g. <10 % in the US and 30-40 % in the EU)6 and the deteriorating value of plastics with repeated secondary recycling, all plastics eventually become waste. The last and most underutilized form of recycling is tertiary recycling, the degradation or depolymerization of plastics into useful chemicals or materials. In the last year alone, numerous high profile editorial and review articles have appeared in Science7,8,9 and Nature6,10 emphasizing the incredible potential of chemical (tertiary) recycling as means of reducing plastic waste and as a new, sustainable chemical feedstock for the polymer (plastics) industry.

The challenge of chemical recycling is immediately evident: plastics have been expertly designed to be highly durable and chemically resistant, and thus, plastics cannot be easily transformed chemically. Ideally, polymers used in plastics could be depolymerized to monomer for subsequent repolymerization. For condensation polymers, such as polyethylene terephthalate (PET), the reverse of the polymerization reaction is the addition of a small molecule to the polymer to reform monomer. While completely reversible on paper or in theory, such depolymerization strategies have had limited success for PET.

Reacting the polymeric PET material with protic reagents (e.g. amines, alcohols) followed by hydrolysis to give monomers that can be repolymerized, if of sufficient purity (Figure 3), requires high temperature (250-300 °C) and high pressure (0.1-4 MPa) conditions unless additives, such as strong acids and bases or metal salts, are used.11 The action of many additives is not well understood, thus precluding rational improvement of the system. Hydrolysis of PET itself, especially at neutral pH, is the most challenging approach to PET chemical recycling as water is a relatively poor nucleophile. Hence stronger nucleophiles, such as ethylene glycol, are preferred.

Figure 3. Depolymerization of PET by glycolysis.

One practical problem in the chemical recycling of any plastic is its insolubility. Phase transfer catalysts –  species capable of transferring from one phase to another – have been used to address the insolubility of PET12 and have permitted the direct hydrolysis of PET at operating temperatures as low as 80 °C, as in the work of Karayannidis and coworkers (Figure 4). The phases in these systems are the insoluble PET polymer (the organic phase) and the basic solution (the aqueous phase) surrounding it.13

Figure 4. Phase transfer catalyzed hydrolysis of PET (catalyst shown in blue).

Addition polymers, such as polypropylene (PP) or polyethylene (PE), cannot be depolymerized to monomer form using the above strategies as their polymerization does not involve the loss of small molecules. Until very recently, the best end-of-life purpose for the majority of plastics has been energy recovery through incineration. The work of Huang and coworkers on the chemical degradation of PE plastics is a break-through for the field of plastic recycling. While previous studies have reported that thermolysis of PE yields poorly defined mixtures of hydrocarbons, these authors have found a remarkable, highly targeted method for converting PE to a narrow distribution of fuels (3 to 30 carbons in length) using a dehydrogenative metathesis strategy (Figure 5).14 The homogeneous iridium catalysts employed were previously reported in the literature for alkane dehydrogenation (step 1) and hydrogenation (step 3), but no such polymer substrates had apparently been attempted for main-chain dehydrogenation. Similarly, the authors used a previously-established rhenium oxide/aluminium oxide catalyst for olefin metathesis (step 2).

Figure 5. The transition-metal catalyzed degradation of PE to liquid fuels reported by Huang and Guan (catalysts shown in blue).14

The chemical recycling of PET by phase transfer catalysis and of PE by dehydrogenative-metathesis have very little in common with one another on a technical level. What unites these two strategies is the desire to transform the problematic, highly abundant and inexpensive resource that is waste plastic into useful commodities. Perhaps more importantly, these two examples both take revolutionary approaches to old problems through inspiration from fundamental research and parallels found in small molecule catalysis. Rethinking the plastic problem into a challenge for catalysis, rather than solely a call for clever materials design, is critical if we wish to reduce the threats that waste plastics pose to our health and our environment.

References:

  1. Tavazzi, L., et al., The Excellence of the Plastics Supply Chain in Relaunching Manufacturing in Italy and Europe, The European House, Ambrosetti, 2013 (as cited in Bühler‐Vidal, J. O. The Business of Polyethylene. In Handbook of Industrial Polyethylene and Technology; Spalding, M. A.; Chatterjee, A. M., Eds.; John Wiley & Sons: Hoboken, NJ, 2017; p. 1305).
  2. Mote Marine Laboratory Biodegradation Timeline; 1993. Available from: https://www.mass.gov/files/documents/2016/08/pq/pocket-guide-2003.pdf ; accessed July 10, 2018.
  3. Image sources: Image sources: (Plastic recycling symbols) http://naturalsociety.com/recycling-symbols-numbers-plastic-bottles-meaning/ ; (PP) https://www.screwfix.com/p/stranded-polypropylene-rope-blue-6mm-x-30m/98570 ; (LLDPE) https://www.polymersolutions.com/blog/differences-between-ldpe-and-hdpe/ ; (HDPE) https://chemglass.com/bottles-high-density-polyethylene-hdpe-wide-mouths ; (PVC) https://omnexus.specialchem.com/selection-guide/polyvinyl-chloride-pvc-plastic ; (PET) https://ecosumo.wordpress.com/2009/06/04/what-does-the-recycle-symbol-mean-part-2/
  4. Andrady, A. L. Journal of Macromolecular Science, Part C: Polymer Reviews, 1994, 34(1), 25-76.
  5. Hopewell, J.; Dvorak, R.; Kosior, E. Trans. R. Soc. B, 2009, 364, 2115–2126.
  6. Rahimi, A.; García, J. M. Nature Reviews Chemistry, 2017, 1, 0046.
  7. MacArthur, E. Science, 2017, 358 (6365), 843.
  8. García, J. M.; Robertson, M. L. Science, 2017, 358(6365), 870-872.
  9. Sardon, H.; Dove, A. P. Science, 2018, 360(6387), 380-381.
  10. The Future of Plastic. Nature Communications, 2018, 9, 2157.
  11. Venkatachalam, S.; Nayak, S. G.; Labde, J. V.; Gharal, P. R.; Rao, K.; Kelkar, A. K. Degradation and Recyclability of Poly (Ethylene Terephthalate). In Polyester; Saleh, H. E. M., Ed.; InTech: London, 2004; p. 78.
  12. Glatzer, H. J.; Doraiswamy, L. K. Eng. Sci. 2000, 55(21), 5149-5160.
  13. Kosmidis, V. A.; Achilias, D. S.; Karayannidis, G. P. Mater. Eng. 2001, 286(10), 640-647.
  14. Jia, X.; Qin, C.; Friedberger, T.; Guan, Z.; Huang, Z. Science Advances 2016, 2(6), e1501591.

Embodied Energy and Solar Cells

Embodied Energy and Solar Cells

By Devon Holst, Member-at-Large for the GCI

Embodied energy is the sum of all energy consumed in the production of goods and services. Knowing the amount of energy something ‘embodies’ is useful when assessing the environmental impact of comparable goods and services as well as assessing the utility of technologies that produce or save energy. If a device intended to save energy embodies more energy than it will save over the entirety of its use, the product is considered to be unfavourable. A net energy loss would be the result of its application.

It is important to consider the embodied energy of renewable energy technologies to ensure there is a net energy gain. I am going to follow the production process of silicon solar cells as an example of how energy can be embodied into a product. To be effective, the embodied energy of a solar cell must be less than the total energy it produces. There are many processing steps needed to assemble a solar cell where the embodied energy should be kept to a minimum. Some of the largest sources of embodied energy in silicon solar cells are described below.

Devon_blog 1

Silicon Processing (Additional embodied energy: 460 kWh/kg)

Carbothermic reduction of quartz sand (silicon dioxide) is used to produce metallurgical grade silicon. This process consumes 20 kWh/kg of metallurgical grade silicon produced. Metallurgical grade silicon must then be further refined to electronic grade silicon through a reaction with hydrochloric acid at 300 oC followed by treatment with hydrogen gas at 1100 oC. This process consumes 100 kWh/kg of electronic grade silicon. This silicon is then melted at 1400 oC and crystallized, consuming 290 kWh/kg of silicon single crystal. This form of silicon is suitable for use in a solar cell. After accounting for losses of material during each step, these processes embody 460 kWh of energy into each kg of silicon single crystal.1

Solar Cell Production (Additional embodied energy: 120 kWh/m2)

The single crystal of silicon is sliced into wafers with a multiwire saw resulting in a 40% to 50% loss as dust. Following this, a sequence of high temperature diffusion, oxidation, deposition, and annealing steps are performed. This adds 120 kWh/m2 ­­­of embodied energy to the solar cell.1

Module Assembly (Additional embodied energy: 190 kWh/m2)

A module consisting of a glass front panel, an encapsulant, the solar cell, copper ribbon, a foil back cover, and an aluminum channel is then assembled. 190 kWh/m2 of embodied energy is added during assembly.1

Support Structure (Additional embodied energy: 200 – 500 kWh/m2)

The module is then typically installed in a field or on a rooftop. In a field, the module needs to be supported by concrete, cement, and steel. Construction and materials add 500 kWh/m2 of embodied energy. Rooftops have an existing support structure reducing the embodied energy of this aspect to 200 kWh/m2.1

Miscellaneous Components

Beyond the former sources of embodied energy there are many other components in an operational solar cell. An inverter, wiring, and a battery are a few examples of these components. Depending on the components needed, this will add a variable amount of embodied energy.1

Devon_blog2Emerging technologies such as perovskites and organic solar cells often have much lower embodied energies than their silicon counterparts. Material processing methods and the amount of material necessary to produce a solar cell are a couple of the major factors that account for the difference in embodied energy of these technologies.1,2 There are, however, many other factors that make a solar cell viable for large scale energy production which when considered in aggregate currently favour silicon solar cells. It is likely that multiple solar energy technologies will thrive in the future as each has unique characteristics making one more applicable to a given situation than another.1,3

The energy payback time of a given solar cell is calculated by dividing embodied energy by energy output per unit time. This is the amount of time a solar cell must operate before it generates the same amount of energy as its embodied energy. Silicon solar cells have a 1.65 to 4.12 year energy payback time, while some organic solar cells and perovskites have energy payback times of less than half a year.4,5

Embodied energy is part of an even broader picture. A picture that captures the energy used to recycle or dispose of something and the energy associated with environmental impacts incurred through goods and services in any way. The picture is complex, but a deep understanding of it is necessary in order to make decisions that are conscious of the future.

I wonder how much energy I embody…

References:

1) Nawaz, I.; Tiwari, G. N., Embodied energy analysis of photovoltaic (PV) system based on macro- and micro-level. Energy Policy 2006, 34 (17), 3144-3152.

2) Anctil, A.; Babbitt, C. W.; Raffaelle, R. P.; Landi, B. J., Cumulative energy demand for small molecule and polymer photovoltaics. Progress in Photovoltaics: Research and Applications 2013, 21 (7), 1541-1554.

3) Snaith, H. J., Perovskites: The Emergence of a New Era for Low-Cost, High-Efficiency Solar Cells. The Journal of Physical Chemistry Letters 2013, 4 (21), 3623-3630.

4) Espinosa, N.; Hosel, M.; Angmo, D.; Krebs, F. C., Solar cells with one-day energy payback for the factories of the future. Energy & Environmental Science 2012, 5 (1), 5117-5132.

5) Gong, J.; Darling, S. B.; You, F., Perovskite photovoltaics: life-cycle assessment of energy and environmental impacts. Energy & Environmental Science 2015, 8 (7), 1953-1968.

Image Sources:

  1. Solar panels (https://commons.wikimedia.org/wiki/File:SolarparkTh%C3%BCngen-020.jpg)
  2. Embodied energy (http://www.paveshare.org/library/embodied-energy)

Green Chemistry Principle #6: Design for Energy Efficiency

By Trevor Janes, Member-at-Large for the GCI

6. Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.

In chemistry (and in life) we need energy to do work. Every task we do in the lab requires energy: whether we’re using a Bunsen burner or weighing out a reagent or dissolving our favourite compound, in all cases we’re using energy in some form.

In the lab, we often need to change the pressure and temperature of experiments, and this uses a large amount of energy. Ideally, we would perform all reactions at ‘ambient’ conditions – room temperature and atmospheric pressure – in order to minimize energy usage.

In Video #6, Julia and David use an energy monitor to see help us see just how much energy is used by everyday lab equipment. They measure a vacuum pump, which is used to reduce pressure, and a hot plate, used to raise the temperature of a reaction.

Julia and David measure the power used by each instrument and calculate the monthly energy bill, comparing the cost and amount of energy to a regular household item like a TV.[1] By doing this they determine the financial impact of the energy requirements of lab equipment. A hot plate uses roughly as much energy as a TV, and a vacuum pump uses more energy than 3 TVs! Just like at home, minimizing the use of equipment in a lab, and turning off equipment when it’s not in use, will conserve energy and save money.

In an academic lab, the amount of energy and its associated cost is modest and may seem insignificant. But on the much larger industrial scale, energy/money savings are multiplied and energy efficiency becomes even more important.

We know that heating a reaction requires energy, but another energy-intensive aspect of lab work that occurs after completion of the reaction is the work-up. “Working up” the reaction means separating our desired product from the other components in the reaction mixture such as solvent and byproducts. We talked about this before in our post for Principle #5.

To remove solvent conveniently we use a rotary evaporator, commonly referred to as a “rotovap,” which involves the combined use of a heat source, vacuum pump, rotating motor, and chiller. The heat, vacuum, and rotation vaporize the solvent and the chiller condenses the solvent vapors into a flask for removal. If you’re curious, we also measured the energy used by the chiller component of the rotovap assembly (see calculations below). If left on all the time, the monthly energy bill for the chiller alone would be $15.60 – the same as 2 TVs – and that’s not including the other rotovap components. If we can develop chemical reactions that avoid solvent removal and/or simplify work-up, we can save energy and money.

justshutit

Our “Shut It” campaign encourages fume hood sashes to stay closed.

Later in the video, we were delighted to host special guest Allison Paradise, Executive Director of My Green Lab who joined us to highlight the importance of minimizing the energy used by chemical fume hoods. As the My Green Lab website explains, there are Constant Air Volume (CAV) and Variable Air Volume (VAV) ventilation systems.[2] In VAV systems, closing the fume hood sash allows the exhaust fan to run more slowly while maintaining a safe flow rate. By closing our sashes in VAV systems we can reduce energy use by 40% or more!

Turning off your TV after you’re finished watching it illustrates the idea behind Principle #6. Just like you care for the environment and save money by being energy efficient at home, we want to minimize the environmental and economic impacts of the chemical processes we do in the lab.

Energy Calculations:

Julia and David measured the vacuum pump to draw 360 W. If we kept it on for one month, this would be 259 kWh. In Toronto, the consumption-based cost of electricity is $0.108/kWh,[1] which makes the cost for one month of vacuum pump use $28.

360 W x (1 kW/1000 W) x (720 h/1 month) = 259 kWh/month

259 kWh x $0.108/kWh = $28

The hot plate heating an oil bath to 110 °C uses 100 W, which amounts to 72 kWh in one month. Using the electricity cost of $0.108/kWh again, the monthly bill for keeping the hot plate on at all times would be $7.80.

100 W x (1 kW/1000W) x (720 h/1 month) = 72 kWh/month

72 kWh x $0.108/kWh = $7.80

Not included in the video is the measurement of a rotovap chiller. This chiller circulates coolant that it maintains at -5 °C, which requires 200 W. This is double the power drawn by the hot plate and represents a monthly energy bill of $15.60.

References:

[1] Cost of electricity and household appliance energy usage, Toronto Hydro: http://www.torontohydro.com/sites/electricsystem/residential/yourbilloverview/Pages/ApplianceChart.aspx

[2] My Green Lab’s explanation of fume hood types and their energy consumption: http://www.mygreenlab.org/be-good-in-the-hood.html