Reducing emissions and air pollution from informal brick kilns

INTRODUCTION:

In many low- and middle- income countries, it is commonly believed that weak state and regulatory capacities limit the ability to reduce pollution and mitigate climate impact. In Bangladesh and across South Asia, most brick manufacturing takes place in informal, traditional coal- fired kilns. These kilns are among the largest sources of greenhouse gas emissions and air pollution, leading to an enormous public health burden.

RATIONALE:

In Bangladesh, efforts to improve the brick kiln industry over the past 30 years have had limited success. Our past work suggests that a correctly operated zigzag kiln (a traditional kiln type that accounts for 81% of the sector) can not only improve efficiency but also increase kiln profits. However, most zigzag kilns in Bangladesh are incorrectly operated, leaving these social and private benefits unrealized. Improving energy efficiency presents an alternative strategy to reduce emissions and pollution while also delivering productivity gains.

RESULTS:

We developed a low- cost intervention to improve the energy efficiency of zigzag kilns and conducted a randomized controlled trial (RCT) of the intervention among 276 kilns in Bangladesh.

Our study included a control arm and two intervention arms (a “technical” arm and a “technical+incentive information” arm). All kilns assigned to both intervention arms received information, training, and technical support to adopt operational improvements that improve fuel combustion and reduce heat loss in the kilns.

These improvements specifically targeted how coal is fed during the firing process and how bricks are stacked inside the kiln, along with several other aspects of operation.

Kilns assigned to the “technical+incentive information” arm also received explicit information regarding the business rationale for incentivizing workers to adhere to the new practices. There was high demand for the intervention, with 65% of intervention kilns adopting the intervention’s recommended firing and stacking practices.

Notably, 20% of control kilns also adopted these practices, bolstering the interpretation that demand was high. There were no differences in adoption between the two intervention arms and no use of incentives or benefits in the “technical+incentive information” arm. We studied the intention- to- treat (ITT) effect of random assignment to the intervention, as well as the impact of the intervention after adjusting for compliance using an instrumental variables (IV) framework. Among compliers, the intervention led to substantial reductions in the amount of energy used to fire bricks (23%) and corresponding reductions in carbon dioxide (20%) and particulate matter with a diameter of <2.5 μm (20%).

These gains were achieved without any evidence of a rebound in energy demand. Kiln owners also benefited financially from the intervention; production of the highest quality category of bricks increased in intervention kilns and spending on fuel per brick declined. The primary costs of the RCT were the training costs and technical support costs throughout the season. Using a social cost of carbon of 185 USD per metric ton to value the reductions in CO2 emissions, we find the benefits of the intervention outweighed the costs by a factor of 65 to 1, and that these reductions were achieved at an average cost of 2.85 USD per ton.

CONCLUSIONS:

Our study demonstrates that meaningful reductions in emissions by traditional kilns are achievable, even in the absence of stronger regulations, if they can be made financially attractive to private kiln owners.

Source: Science 08 05 2025

Why some Hong Kongers live in homes smaller than a parking space

Landlords in Hong Kong, a city with a notoriously high cost of housing, have found they can make more money by dividing a flat into two or more units

Tens of thousands of people in densely populated, land-poor Hong Kong live in tiny dwellings made by dividing up apartments, most smaller than a parking space. It’s an affordable option for students and low-income families but can also mean banging shins in cramped and in some cases substandard living spaces.

The city’s government has proposed new rules that would set minimum standards for such housing units, but residents and advocates for the poor worry that it could drive up rents and make it even harder to hang on in the city. The city’s eventual goal, mandated by Beijing, is to eliminate subdivided apartments over the next 25 years.

Officials are aiming to pass the rules into law within the year. After that, landlords will have a grace period to make their substandard flats meet the bar. The government has promised to assist affected residents in resettlement and adopt a gradual approach in its policy implementation to avoid causing panic.

Here are some of the numbers that illustrate the residents’ living conditions and the proposed policy.

7.5 million Hong Kong’s population in mid-2024

80 square kilometers (31 square miles) How much land is used for housing in the densely-packed territory, according to the city’s planning department

110,000 The number of dwellings created by dividing apartments

220,000 The number of people who live in them

10 square meters (110 square feet) The median size of the units that have been carved out. About one-fourth are less than eight square meters (86 square feet), the minimum size mandated under the proposed rules

12.5 square meters (135 square feet) The standard size of a parking space in Hong Kong

5,000 Hong Kong dollars: or PHP 37,000 the median rent for a unit in a subdivided apartment

33,000 Estimated number of units that would need major renovations under the proposed rules

2049 The year by which China’s central government wants Hong Kong to phase out subdivided units. It will mark 100 years of communist rule in China.

Source: Philstar

Planning the urban climate of the future

What a tree needs to grow and how it affects its surroundings vary from species to species. This makes it increasingly important for cities to adapt the urban tree cover to local conditions.

A team at the Technical University of Munich (TUM) has developed the online tool CityTree. Cities, municipalities and interested individuals can use it to find out how 12 common tree species are growing in 34 German cities and how they will benefit the local climate in the future.

Trees reduce heat stress on hot days, emit oxygen into their surroundings and bind climate-damaging CO2. This adds up to a decisive contribution towards maintaining the best possible quality of life in cities as the world heats up. A team working with the forest scientist Prof. Thomas Rötzer has investigated the advantages of selected tree species for the urban climate and the conditions under which they thrive.

To conduct the study, the researchers measured more than 5,000 urban trees throughout Germany, took samples from them and analyzed their surroundings. The focus was on lime trees, locust trees, plane trees and nine other species that make up 60% of the urban tree cover in Germany.

The data were then used to create an interactive model called CityTree. Access to the tool is free of charge. It is mainly intended for cities and municipalities, but can also be used by ambitious hobby gardeners when planning tree plantings in their own gardens.

Creating virtual trees

Users can define a virtual tree with just a few clicks. After choosing from among 34 cities and 12 tree species and defining such characteristics as soil type, the level of soil sealing and light exposure, the user sees how much CO2 the tree will bind, how much it will cool its surroundings and the quantity of water it will use.

The preview can also reflect various climate scenarios. The period from 1991 to 2000 simulates tree performance in the current climate, while 2003 represents a dry year. For the period from 2081 to 2090, the user can choose between climate scenarios based on 1°C or 4.8°C of global heating.

The data illustrate the importance of detailed planning for urban greenery. Cities like Berlin and Würzburg, with low precipitation and high temperatures, benefit more from plane trees and other drought-tolerant species. A city like Munich, with relatively high rainfall, can plan for species such as small-leaved lime and horse chestnut trees if the tree pit is large enough.

Planning for 2081 starts now

Although 2081 might seem like a long way off, "It is urgent for cities to take action now and critically assess their tree cover. Planting decisions shouldn't be based solely on aesthetics," says Thomas Rötzer.

"A tree has to grow for many years before it has a noticeable impact on urban climate. In the past, cities and municipalities lacked concrete information for planning optimized tree plantings and to assess the performance of existing trees. Through the app, we have converted scientific data into a usable format with practical benefits that can address this urban planning shortfall."

The research team recommends that local authorities develop a systematic overview of their trees. So far, there are only a few resources that would represent an "urban tree cadastre." With this knowledge, cities could establish programs with concrete targets and measures for optimal adaptation to the challenges of climate change.

The research team is currently working toward that objective. Using satellite images, they are surveying the tree population of Munich and assessing its potential growth and the benefits to the urban climate. These data can then be used for the sustainable management of the city's tree cover.

Source: Phys Org