Climate

LCA of carrier Bags

I’m sure this has bothered most of us at some point. It is about the use of plastic bags. Plastic consumption and its environmental effect due to poor biodegradability frequently come under the public discourse. And here is an interesting research report based on the Life Cycle Analysis (LCA) of a few commonly used carrier bags in the UK, published by the Environment Agency (2011).

LCA is a standard methodology to estimate the material, energy usage, and environmental impact throughout a product’s lifecycle (‘cradle to grave’). The study covered only the carriers available from the UK. The material in focus was conventional HDPE, HDPE with pro-degradant additive, starch-polyester (biopolymer), paper, heavy-duty LDPE, non-woven PP and cotton bag.

The end-of-life processes for the different materials included landfill and incineration (for all) and mechanical recycling and composting, where applicable.

The following table contains the energy use and waste generation from 1000 bags of each material.

Bag TypeElectricity
(kWh)		Heat
(from
NG)
(kWh)		Heat
(from
Fuel oil)
(kWh)		Waste
(g)
Conventional HDPE6.151418.4
HDPE + additive6.392426.1
biopolymer17.2494.8
LDPE32.5813.953171.2
Non-woven PP87.755,850
Cotton111,800

The study assumed the reuse of about 40% of all lightweight carrier bags as bin liners.

The next one up was the global warming potential. GWP (excluding primary reuse) for the cotton bag (250 kg CO2 eq.) was more than ten times that of any other bag! It was followed by PP (22), LDPE (7), paper (6), biopolymer (5), HDPE (2.1) with additive and HDPE (2), in descending order. In other words, a cotton bag requires to be used 173 times to match HDPE and PP 14 times.

Here is a summary:

Bag typeSensitivityGWP
(kg CO2 eq)
HDPEBaseline1.578
HDPERecycling1.400
HDPERecycling
(no reuse)		1.785
HDPE
prodegradant		Baseline1.750
biopolymer Baseline4.184
biopolymer Composting2.895
biopolymer Composting
(no reuse)		3.329
Paper bag
(4 uses)		Baseline1.381
Paper bag
(4 uses)		Recycling1.090
Paper bag
(4 uses)		Composting1.256
LDPE
(5 uses)		Baseline1.385
LDPE
(5 uses)		100%
Recycling		1.196
PP
(14 uses)		Baseline1.536
PP
(14 uses)		100%
Recycling		1.292
Cotton bag
(172 uses)		Baseline1.579

To conclude

HDPE bags have the lowest environmental impact among lightweight bags on 8 out of 9 counts.
The starch-polyester (biopolymer) bag has the highest impact in 7 out of 9.
The paper bag needs to be used four times to match HDPE’s global warming potential.
The cotton bag has a greater impact than the HDPE bag in 7 out of 9 categories, even when used 173 times.
The key to reducing the impact is to reuse as much as possible.

Reference

Life cycle assessment of supermarket carrier bags: a review of the bags available in 2006

LCA of carrier Bags Read More »

The Truth that Exists in Mathematical Models

The concept of comparative advantage is something we saw when we analysed international trade as beneficial to both participating countries. Yet, the notion remains highly challenged by the common public. Trade, in their mind, remains a zero-sum game. If I go and sell goods in a foreign country, they lose, and I win.

Similarly, the role that the climate models play in understanding global warming. No matter how hard one tries to prove the fact using charts and equations, the public still requires to hear stories of hardships of extreme weather events to move their views. Mathematical models are inevitable as we are dealing with a complex problem with many factors that are not related linearly to the climate.

Part of the blame for this situation falls on the economists and scientists themselves. Most often, they assume the concepts they develop are simple and intuitive, and those who don’t understand are some less intelligent type.

On the other hand, people grow up hearing exaggerated stories about common sense and simple narratives. Models and equations are too difficult to understand and, therefore, some form of a trick played by the proponent.

The Truth that Exists in Mathematical Models Read More »

Efficiency and Equity

Consider this example:
Andy and Becky are both chocolate lovers. Andy has ten chocolates, and Becky has zero. Is the system Pareto efficient? (Hint: try taking one away from Andy and give it to Becky). The system, at this current state, is Pareto efficient. But not equitable.

Equity means the distribution of goods and services is reasonable to the parties involved. The chocolate lover Becky getting no chocolate is unlikely a reflection of an equitable society!

A market, at a competitive equilibrium, is supposed to be Pareto efficient. And this says nothing about justice. While driving efficiency is a market objective, managing equity is a political decision.

An instrument used by governments to manage this inequity is taxation. For example, in a progressive tax structure, the highest income earner will pay more proportion of their wealth compared to a lower income earner. The expectation is that the distribution of after-tax wealth is fairer than before. But you may argue that taxing is Pareto inefficient as it hurts citizens, more so the people with more wealth.

Efficiency and Equity Read More »

Salamander Reporposed!

Salamanders are fascinating creatures that have drawn plenty of spotlight from biologists due to their significant position in our evolutionary path. These are amphibians, and it was no coincidence that they drew attention, as a missing piece between creatures of water and that of land, from scientists in the 19th century, inspired by the recent theory of evolution.

In one such pursuit, what the famous zoologist and the Professor at the Museum of Natural History in Paris, Auguste Dumeril, found provides a live example of the wonders of repurposing animal functions.

In 1864, Dumeril received six salamanders from a lake in Mexico. They were large adults with feathery gills and aquatic body shapes characteristic of life in water. He kept them together and even had them produce fertilised eggs. The children that came out of the cage shocked the researcher; they showed little resemblance to their parents. No gills and aquatic tail; they appeared like the terrestrial variety.

It was found out much later that there are two pathways of development for the salamander larvae, according to the surrounding environment. The salamander in the aquatic habitat goes through the default pathway, but the one on land undergoes this metamorphosis. We now know the change gets triggered by the amount of thyroid hormone in the bloodstream that activates or kills some cells. Same gene, same creature but a change of environment yielding dramatic change in the appearance of the end product!

Reference

Some assembly required: Neil Shubin

Salamander Reporposed! Read More »

Common Sense Continued

The not-so-hidden secret is that biological innovations never come about during the great transition they are associated with.

Neil Shubin, Some Assembly Required

Another case of common sense is the theory of evolution.

Theorem of evolution

While it is no more topic of debate, thanks to millions of data collected in the last one hundred odd years, the concept of evolution has confused the generations since the day it was proposed.

Evolution of common sense

The first one was the remnants of Lamarckian thinking that essentially assumes that evolution is what an organism aspires and achieves, in its lifetime, to adapt to its environment. For example, a giraffe, in pursuit of high-lying leaves, stretches its neck so much that its child gets her neck a little longer than her mother, and it continues.

The other group is less dramatic with their approach, though commonsensical. Feather occurred to birds because it enabled the birds to fly, which helped them to survive in that environment. Similarly, lungs and limbs happened just about when the water-living creatures prepared to come out to the land.

More and more pieces of evidence proved that this understanding is wrong. The features such as the lungs or the wings were part of predecessor creatures ages before they transformed into their next level. For example, fishes of all species had swim bladders that enabled them to navigate different depths in the water. As genetic studies have later found, the genes responsible for these air sacs are the same that propelled the development of lungs. In other words, when the fish’s successor came to land, it just repurposed the swim bladder for breathing.

Inventions to products

A closer analogy is the example of green hydrogen as a vector of decarbonised energy. Hydrogen production through water electrolysis using renewable electricity such as solar PV is considered a commercial-ready option for a carbon-free energy future. To anybody who followed the history of science, electrolysis is by no means a new technology.

Alkaline water electrolysis technology is more than 120 years old. It has been serving the niche market of caustic and chlorine until now.

Similar story for solar PV. Bell Labs announced a solar battery in 1954 that could produce electricity whenever a thin slice of silicon was contacted by sunlight, being celebrated as a miracle device by the leading newspapers of that time. At the time of its invention, it was so expensive that Bell Labs calculated a cost of $1.5m to power one home using their technology!

But nothing happened for another 65 years!

Repurposing under societal pressure

This chemistry of evolution, where the ingredients were made in the distant past, but mixing happens only today, has confused people and led to creating two bands of commentators. The first group, the Vaclav Smil-type, develops some allergy to “high-tech worshippers” and claims whatever happens today was a result of the 1880s. The second group are mesmerised by the speed at which discoveries are happening right in front of their eyes. Both got carried away by the chemistry of evolution.

Common Sense Continued Read More »

Climate Change and Common Sense

To all the people in the northern hemisphere who are currently reeling under extreme heat waves: your assessment of global warming is correct, but not for the reasons you think you are seeing.

Common sense is a general intelligence that enables a person to manage concrete everyday situations. It is common sense to switch the power off before removing a bulb from its holder. Wearing a protective glove before touching the metal pot on the kitchen hob is another.

In a survey conducted in Australia between 2010-14, 22% of the respondents thought climate change was not happening. When specifically asked about what their opinions are based on, about 37% of them attributed to common sense. It might sound absurd that about 20% of the people who believed in human-induced climate change also attributed their belief to common sense. And the views of both parties are not surprising. Phenomena such as global warming are understood only through the laborious examination of scientific data from hundreds of sources through the lens of mathematical models. And there is nothing commonsensical about it!

The offspring of hindsight

It is a fact that some of the lessons learned from science can later become part of the common sense knowledge in everyday life. But trusting that the opposite is also true is dangerous. We have seen multiple examples of logical fallacies previously. Availability bias is one of them. For a climate sceptic, the last year’s winter might be the guiding principle, whereas, for a climate believer, it’s the heat wave of this summer. One can prove either of these as instances of random events, even when the number of hard facts on climate change is irrefutable.

Overdependence on experience

Common sense is primarily a manifestation of personal experience; science, on the other hand, is a rational, evidence-based approach that operates through the collaborative actions of hundreds of trained minds. While individual scientists are fallible mortals with cognitive biases and beliefs, the rigour of methodology – validation and falsification – known as the scientific method, by its community elevates science from those shortcomings.

Climate Change and Common Sense Read More »

The Weight of Energy Transition

Global warming concerns everybody because it triggers climate change or the long-term change in the average weather patterns.

Not a small problem

The world needed 600 EJ (ExaJoules of energy) in 2019. So what is an ExaJoule? It is an energy unit, which equals 1018 Joules (1 followed by 18 zeros). To put it in perspective, the energy consumed by your 10 W LED bulb in one hour is 36000 Joules. Another unit to describe energy is TWh (terawatt hour). 600 EJ is approximately 167,000 TWh.

So, what is the issue with this energy? Out of this 600, 490 are directly connected to CO2 emissions. Or that energy is produced by burning fuels containing carbon atoms in it – you call it coal, crude oil or natural gas. Let’s look at the split in the year 2019.

OilCoalNatural
Gas		BiofuelsNuclearHydroWind
Solar
18716214057301513

The Weight of Energy Transition Read More »

What happened to the Past Climate Predictions?

We have seen the role of climate models to understand the magnitude of global warming. Almost all of the narratives of catastrophe from the climate commentators go back to the output of climate models. And projections from these models play a crucial role in shaping our collective consciousness and aligning global policymaking to fight against this human-made problem.

Models also contribute to why the subject of global warming gets criticism from the sceptics. To most non-physicists, mathematical models represent fantasy, unconnected to reality. Also, projections are forward-looking, and it is easy to cast doubts in public minds for its alleged function as a crystal ball. Calling such people anti-science is easy but not entirely justified; after all, science too calls for the same; get the evidence and validate your predictions. So how do we validate a model prediction for the future?

Look for the past predictions!

Hausfather and others published a paper in the geophysical research letters in 2019 that exactly went for this. The work looked at various models published between the 1970s to the late 2000s. And what did they find? The team have gathered about 15 model predictions from the past and compared them with the observed data. They found that the predictions were well within the margin of errors of the observations. The models of the 70s, 80s and 90s were pretty accurate to predict the future, which is past by now!

What is a climate model?

A model gives a connection between an input and an output. It’s achieved using the physics of the process and represented through the language of mathematics. In the context of climate change, concentrations of CO2 in the atmosphere is the input, and the temperature rise (or fall) is the output. A typical model estimates the reason for the temperature change, i.e., the radiative forcing or the change in energy flux (the incoming – outgoing energy) on the planet. In other words, if the outgoing is less than the incoming, the temperature rises; otherwise, it falls, simple!

Why is this no news?

There are many reasons why a good match between a model and observations never makes it to the news. But, before getting there: why do you expect the predictions made by the collaborative works of 100s of top scientists to go wrong in the first place? We will explore the answer in another post. Now, let’s come back to why they didn’t become headlines. First, predictions happen today (which attracts news), but the data arrive 5-10 years later. By then, you may have forgotten about the original work! Secondly, matching an expectation does not make it sensational for the news. Imagine this news: “NASA scientists verified the physics of radiative forcing, again”! Third, a good match like this is more of a nuisance to the people who want to believe that climate change isn’t real (or who worry about the need to change the current lifestyle).

One such example is the projections made by NASA’s Hansen et al. in 1988. That story, in another post.

References

What happened to the Past Climate Predictions? Read More »

When the Dominant Strategy Leads to Doom

We have seen in the previous post that from a country’s standpoint, it is more advantageous to do nothing for the climate. And let others work for the betterment of you! We’ve also seen that others, too, playing their little games, will follow suit, each finding their equilibrium to the detriment of the whole planet. In other words, individual rationality leads to collective irrationality.

The Paris Climate Accord

The role of the Paris Accord is to force countries and bring them to the non-dominant strategy {contribute, contribute}. It can be done in the following ways.

First, the Paris Agreement is legally binding. So all the signees have to contribute. But here is the catch: the amount of contribution is determined by the individual country through what is known as Nationally Determined Contributions (NDC).

The second option is to provide incentives. The Paris Agreement provides the framework for financial, technical, and capacity building for those who need it. Financial support is necessary to achieve capacity building, which, in turn, will reduce the cost through a feature known as the learning rate.

The third option is to impose a cost on non-compliance. As part of the Enhanced Transparency Framework (ETF), countries are required to report back in 2024 and show the actions taken. The process can induce a moral cost to the participating countries, inducing the required push to follow up on promises with actions. Moreover, the measurement, reporting, and verification are legally binding.

Paris Agreement: UNFCC

When the Dominant Strategy Leads to Doom Read More »

The Game Called Climate

International cooperation on climate change is an example of game theory with a Nash equilibrium and a dominant strategy. Let’s look at the problem from a country’s viewpoint and construct the payoff matrix. We call it the country MY.

The premise is that the climate crisis is real, but the solution is costly because it requires developing new technologies. If neither the country MY nor the rest makes any attempt to invest, the game ends in total calamity: {(MY:-10), (RE:-10)}. On the other hand, if country MY remains a passive free-rider and the rest of the world does the job, the former gets the maximum benefit (MY:12). On the other hand, if country MY makes all the effort, the payoff will be (MY:-15) in great losses for them. Finally, if everybody cooperates according to their respective capacities, all of them will benefit {(MY:10),(RE:10)}. The payoff matrix is

Country MY
Country MY
doesn’t contribute		Country MY
contributes
The RestThe rest
doesn’t contribute
MY: -10, RE: -10MY: -15, RE: 12
The rest
contributes		MY: 12, RE: 8MY: 10, RE: 10

Country MY calculates that it is better placed by not acting, irrespective of what the rest does. They also anticipate that, in such a scenario, the rest will lose more by not working. From an individual country standpoint, this logic of not participating makes it economically advantageous.

But there is an error in this thinking. Any (or all) of the countries in the rest can also follow Country MY’s suit. It leads to a total failure, and no one benefits {-10, -10}

The Game Called Climate Read More »