Smog over Delhi during a severe air-pollution episode — the recurring condition every intervention in this piece is measured against. Source: Wikimedia Commons contributor, Wikimedia Commons, CC BY-SA 4.0.

The Centre for Research on Energy and Clean Air's analysis of CPCB's own Continuous Ambient Air Quality Monitoring Station data, reported by The Wire, put Delhi's average PM2.5 concentration at 163µg/m³ across the 1 October 2025–28 February 2026 winter season — against India's own annual National Ambient Air Quality Standard of 40µg/m³ and the World Health Organization's annual guideline of 5µg/m³. Of the season's 151 days, CPCB classified 18 as "severe," 87 as "very poor" and 24 as "poor"; only 22 days fell into "moderate," "satisfactory" or "good" combined. Whatever intervention gets discussed below, this is the scale it has to move the needle against: a pollution load roughly four times the domestic standard and more than thirty times the global one, sustained across five months, not a handful of bad days around Diwali.

Delhi's most visible anti-pollution structure is the 24-metre smog tower at Connaught Place, inaugurated by then-Chief Minister Arvind Kejriwal on 23 August 2021 at a reported cost of ₹25 crore. It runs 1,200 fans through HEPA H14 filters rated to remove PM2.5 down to 0.3 microns, with a stated design capacity of 1,000 cubic metres of clean air per second. It has also been studied more than almost any comparable structure in India, and the studies do not flatter it. IIT Bombay's own final assessment, submitted in October 2023 after a 2022–24 monitoring programme run jointly with CSIR-NEERI, found efficiency of roughly 48–56% within the first 20 metres of the tower — a figure that fell sharply with distance and showed no significant improvement to ambient air quality beyond a small radius. The Delhi Pollution Control Committee's own later assessment, after two years of operation, found the tower mitigated pollution by at most 17% within a 100-metre radius. The Supreme Court's own monitoring committee called smog towers, this one included, "costly experiments with limited utility" in 2023. The tower has also been reported shut down more than once amid disputes between the Delhi government and the DPCC over who authorized stopping it.

None of that stopped the idea from spreading. On 12 November 2025, Jaipur became the first Indian city to install street-level air purifiers, placing four eight-metre "PAMARES"-style towers at Rambagh Circle, Ajmeri Gate, Jawahar Circle and Tonk Road, each reportedly rated to filter up to one million cubic metres of air an hour — but, per the same coverage, each unit's actual effective radius is only about 40–50 feet. The public and expert reaction was immediate and largely negative, with critics arguing, in effect, that the Connaught Place lesson had not been learned: a purifier that treats a traffic circle's air within arm's reach does nothing about the vehicle exhaust, industrial emissions and crop-residue burning that produce the pollution load in the first place, and Jaipur has offered no independent third-party efficiency study of its own yet.

Delhi Metro has converted eight pillars along its elevated Blue Line between Mandi House and Pragati Maidan into vertical gardens, and has separately announced plans to green roughly 70 more pillars around the Dhaula Kuan flyover on its Pink and Airport lines. The South Delhi Municipal Corporation ran a parallel project at the Savitri flyover, with more than a dozen South Delhi flyovers reportedly planned to follow. Advocates cite figures — a four-storey vertical garden removing around 130 grams of particulates and filtering roughly 40 tonnes of greenhouse gases, one square metre generating a year's oxygen supply for one person — that this piece could not trace to a peer-reviewed or government-verified source; they appear to originate with advocacy and lifestyle coverage rather than an engineering study, and should be read as claimed figures, not measured ones.

What is independently documented is the maintenance problem. At the Rani Jhansi flyover, vertical-garden installations on concrete pillars were reported dried out and dead from inadequate water supply and heat exposure — a specific, named failure of exactly the kind that undermines any claimed benefit calculated for a garden that is alive. A vertical garden's air-purification value, whatever it actually is, only exists for as long as the plants in it do; Delhi's own record includes both maintained installations and ones that failed within a few years of installation.

"The Army is planting trees in Delhi" is technically true of at least two very different things, and conflating them overstates what either one is actually doing.

The first is ceremonial: the Indian Army's nationwide "Ek Ped Maa Ke Naam" plantation drive, run in conjunction with a "Go Green Station" initiative across cantonments, had reportedly planted more than 42 lakh trees nationwide since the campaign's launch, with one visible event held at Shekhawati Lines in Delhi Cantonment. That figure is Army-wide, across every cantonment the campaign touched, not a Delhi-specific count — the Delhi event was one plantation ceremony among many, not a distinct large-scale Delhi programme in its own right. Delhi's civic version of the same "Ek Ped Maa Ke Naam" campaign, run by the Delhi government rather than the Army and launched at the Central Ridge and Nanakpura Ridge by the Union Home Minister and Delhi's Chief Minister, had reached 37.99 lakh of a 70-lakh-sapling target — a little over half — as of the most recent reporting found for this piece.

The second is structural and far older: the Territorial Army's Ecological Task Force (ETF), described by multiple sources as the world's first ecological battalion, raised in 1982 after agronomist Norman Borlaug reportedly suggested to then-Prime Minister Indira Gandhi that the Army be used to restore the degraded Shivalik hills. Its first unit, 120 Infantry Battalion (Territorial Army) Ecological Garhwal Rifles, began reforestation work in Uttarakhand's Doon Valley that year. Ten ecological Territorial Army battalions now operate, each sponsored by a different state government, and as reported by outlets including The Better India and The Quint, they have collectively planted an estimated 6 crore saplings across roughly 70,000 hectares with a claimed 70–80% survival rate over more than four decades. Delhi's own contribution runs through ETF 132 Battalion (Rajputana Rifles), deployed under a project the Delhi government sanctioned in 2000–01 with Delhi University's Centre for Environmental Management of Degraded Ecosystems, to rehabilitate roughly 2,100 acres of the degraded Bhatti mines and a further 1,400 acres near Dera Mandi — former quartzite quarries on the Aravalli ridge in the city's south, not the ceremonial plantation sites further north.

Compiled from ANI, the Ministry of Information & Broadcasting's own "Ek Ped Maa Ke Naam" achievements note, Tribune India, The Better India, The Quint, GKToday and forest.delhi.gov.in. Nationwide ETF figures and survival rates are as reported by secondary press coverage citing the Territorial Army; this piece did not locate a single official, consolidated Territorial Army dataset behind them.

For anyone actually looking to plant something rather than read about others planting it, Delhi's practical infrastructure sits alongside both programmes rather than inside either: Brar Square Nursery, a government-run Delhi Forest Department nursery on Mahatma Gandhi Road inside Delhi Cantonment, is one node in the department's wider free-sapling network, alongside the department's own "Dilli Free Tree" e-seeding portal, which lets residents, schools and resident welfare associations request indigenous saplings suited to Delhi's soil directly.

The most direct complication to the afforestation narrative above sits on the Ridge itself. Delhi's Central Ridge, an 864-hectare offshoot of the Aravalli hills made up of dry forest, grassland and rock outcrop, has been the site of what reporting from Scroll.in and Down To Earth describes as a themed-park restoration that clears existing, if degraded, forest to plant a new one: DDA's Nyaya Vatika project, covering a reported 30–40 acres, was created in place of a more diverse natural ecosystem, and secondary reporting describes visibly high mortality among the saplings planted in the cleared plots — consistent with what typically happens when saplings go into denuded soil, inappropriate microsites and little shade, rather than an intact forest floor. Separately, the Supreme Court has proposed a detailed inquiry into the Delhi Development Authority's role in tree felling elsewhere on the Ridge, and the Delhi High Court has issued a contempt notice to DDA and forest officials over the felling of roughly 1,000 trees.

None of this means the Ridge afforestation drives described in Section 4 are fabricated — the Army and Territorial Army plantation activity documented there is real. It does mean that "trees are being planted on the Ridge" is not, by itself, evidence the Ridge's ecology is improving: the same institutional activity that produces plantation photo-ops can, per this reporting, also involve clearing standing forest to make room for a more manicured one, with the new plantings dying at a visibly high rate. This piece could not directly fetch the Scroll.in or Down To Earth articles behind this section during research (both returned blocked-egress errors); the account above is reconstructed from search-engine summaries of their reporting, not a direct read of either piece.

The newest entrants to this space are not towers or trees but bioreactors, and there are now enough Indian companies pitching microalgae for air and carbon capture that they're worth comparing against each other, not just against smog towers. Zaara Biotech, a Thrissur-based biotechnology startup founded in 2016, markets "Obelia," an algae- and seaweed-based "oxygen bar" it describes as India's first algal artificial carbon-trapping system, presented at COP28 in Dubai in 2023 as one of 22 participating startups. Carbelim, a Kochi-registered, IIT Madras-incubated startup founded in 2023 by Karthika Gopi, Gopakumar Gopalan and Rahul Babu Achakkottil, has raised a $355,000 pre-seed round and is developing a "PureAir Tower" and a building-integrated "Biomimetic Facade" panel, with R&D and production based in Coimbatore. AlgaeTree, launched in 2024 by Shakti Sagar and Sameer Sagar under the Mushroom World Group umbrella in Bhopal, is the only one of the three with a named public deployment: its solar-assisted microalgae unit was inaugurated on 1 May 2026 by Madhya Pradesh Cabinet Minister Vishwas Sarang at Swami Vivekananda Park under Bhopal's Smart City programme, and the company announced in July 2026 that it had expanded to Indian Oil Corporation's Gujarat Refinery in Vadodara and to Amanora Park Town, a township in Maharashtra.

"Known deployment" means a named, dated, public site this piece could confirm through press coverage — not a lab prototype or a funding announcement. On that measure, AlgaeTree is currently the most advanced of the three, though the CO2-capture figure behind that deployment is still a company claim, not a study result. Whether a solar-assisted microalgae unit's real-world capture rate holds up under Delhi's actual winter conditions — lower light, lower temperatures, far higher ambient particulate load than Bhopal or a refinery campus — is a separate, untested question none of the coverage located for this piece addressed.

IIT Delhi's own air-pollution work runs through two separate channels that shouldn't be confused with either the algae ventures above or each other. The Arun Duggal Centre of Excellence for Research on Clean Air (CERCA), inaugurated on 16 February 2018 by then-Lieutenant Governor Anil Baijal after alumnus Dr Arun Duggal pledged roughly ₹5 crore alongside IIT faculty and students, is a research and monitoring body: its stated mission is generating the scientific source-apportionment data Delhi's government needs to design policy, not deploying purification hardware itself. This piece could not directly access CERCA's own website during research to confirm its current active project list, so the description above is limited to what independent reporting on its founding and mandate could confirm. Separately, IIT Delhi's incubation arm (FITT) has produced consumer-facing air-pollution startups at a much smaller scale: NanoClean Global, founded in 2017, makes a roughly ₹10 nasal filter reportedly used in 30 countries plus AC-mounted nanotechnology filters that convert an existing air conditioner into a rough air purifier; ShudhVayu Innovations has an FITT-incubated, vehicle-mounted device concept aimed at removing PM10 in bulk. Both are real products addressing personal or vehicle-level exposure, not the city-scale ambient air problem Sections 1–5 describe, and neither is an algae technology.