In the post-war decades, the hegemony of cow juice went unchallenged. In an aptly bovine manner we drank from the cup provided by the Milk Marketing Board and others, drinking in the stuff about calcium gain and nutrients. Then came the backlash. An article by Anne Karpf in 2003 started with the immortal line "Does God's own PR company handle the account for milk?", before exposing alleged trumped-up health benefits, allergies, intolerances and animal exploitation.

But is the sacred cow now returning in a greener colour? Last week there was much celebrating of the fact that dairy farmers are well on the way to meeting the goals of the Milk Roadmap l and even ahead of environmental targets for 2010. Then Dairy UK announced it is chumming up with the Carbon Trust so that in no time at all you'll be able to buy a pint with a carbon footprint label on the bottle.

Actually it feels good to give this industry praise for a change, given that it's as if the word "beleaguered" was invented to precede "dairy farmer". Despite various initiatives to raise farm gate milk prices, they remain at around 1983 levels. A few months ago the independent milk co-op , the Dairy Farmers of Britain, filed for administration. Farmers are still leaving the industry, milk production is declining, the national herd is shrinking.

Why should this bother me? Because I live in fear of being left reliant on disgusting UHT milk. A now-forgotten government proposal from 2007 suggested that 90% of fresh milk production switch to UHT in the name of fewer emissions. Despite the fact that UHT is an acronym for Ultra Heat Treated, the energy expended during this treatment is nothing compared to the production of conventional milk with its processing, refrigeration and carting around the country.

Cutting the greenhouse gas emissions of conventional fresh milk is no mean feat. If you compare the ratios of global warming potential (GWP) to primary energy consumed, producing a cow comes in about 50% higher than a pig or chicken. And the methane cows emit remains in the atmosphere 21-23 times more effectively than CO2. However, as Peter Griffith, the director of Farming Online pointed out to me, it's worth considering that the amount of methane a herd emits depends on the breed and what it eats — different diets can result in less methane.

Fortunately, dairy farmers have a vested interest in going green: they want to cut emissions if only to lower their electricity bills. Research in Ireland found that it takes 3.59 to 6.7kWh of electricity week to milk each dairy cow because of the milking, the cooling of the milk, and the heating of the water to hot wash the machines.

But there's more to dairy milk's impact than electricity and methane. Conventional dairy farming depletes nutrients in the ground and uses huge quantities of fertilisers — fertilisers account for roughly 1% of the world's total energy consumption — which is why some people argue the green route is to go for organic milk. OMSCo, a co-op of 300 UK organic dairy farmers, also argues that the clover-based pastures used by organic farmers "fix" nitrogen (a natural fertiliser). It adds that organic herds forage more than conventional dairy farmers, suggesting less feed - including soya - needs to be imported for organic milk.

What about packaging? Reader Ann Gee emailed me to say she's switched to organic milkbut it comes in a plastic carton as opposed to her old glass milk bottle. And the mere mention of milk bottle reminds me of the plastic pouch and jug brought out in 2007 by Welsh organic milk cooperative, Calon Wen. Does anybody still have that plastic jug in their fridge? When I asked around at the time of the plastic jug launch, packaging expert Rob Holdway warned that a niche product would have problems making a big impact. Ann , I think that now applies to the good old glass milk bottle. It has been eclipsed by the HDPE plastic bottle where the collection and recycling system has become quite efficient: about 35% of HDPE is now recycled into new bottles. Josh Brooks, editor of Packaging News, also emailed to remind me that the Milk Roadmap sets targets for using recycled content in milk bottle packaging - 10% by 2010, 30% by 2015, 50% by 2020.

Finally, several readers have asked me about the environmental impact of non-dairy alternatives. Ultimately, the relative impacts of non dairy milk – hemp, soya, oats, rice, almonds etc – are probably lower than the environmental footprints of dairy milk, but there aren't any conclusive evaluations to back this up yet. User SerenAur reminds me that if I'm going to do a "comparison with soya milk, please bear in mind that a litre of dairy milk may use more soya in production than a litre of soya milk. So don't forget the impact of the cattle feed." It's a good point, but as I've written previously, don't forget soya has its own problems with processing chemicals.

As a consumer, I'm a bit of a non dairy novice – although I've ordered a "Hemp Milk Maker" and will report back on how it goes – so I'd love to hear your recommendations in the comments below for the best non-dairy alternatives.

Here's what Lucy wrote when asking for your help on 7 August: