My last grow turned out alright. The buds were den...

A lot of it is genetics like @Hashy said. I have grown dense buds like a dispensary at home with shit equipment. So it was all on the genetics at that point. heavy leaning indicas tend to do that more. Supplemental lighting from sides and bottom and CO2 can help. but also so can PGR's and other shit they add into the grow. HID lighting like HPS/CMH was king of dense buds and LED's just are not the same from all the guys I talk to who used to grow from the old days. they love the HID's but the hydro cost is a setback and the heat issues.

Holdimg your most light for fattening. Ppl c pre flower and turn up their light. Pre flower is a growth phase. What's needed is perfect environment to build stigmata. Then this stigmata (pistils/shoots/internodes been tight) will form calyxes during fattening. This is when your light should be high and giving sugars/enzymes/high pk boosters. Good Defoliation methods. Lst; hst and other methods learnt over time give good Looking bud. But bud is bud. And once u grow a plant right its strength should be there regardless of its size and density of buds.

Well Ur A Grade bud. Most is grown outdoors. And with 400co2 ppm. Yes strong light but a plant can only use so many photons in reg environment Yes, co2 enhances buds in fattening But A grade bud can be done. A few grows Understanding DLI/VPD/GOOD FEEDING/PHASES OF PLANTS AND HER NEEDS MET/NO STRES/ GOOD LIGHT/VENTILATION. Homegrown is HM. But id pit some of my strains up against any A grade now. Yes it took me a while to be able to grow good weed. Research and trying and a passion and A grsds bud is more than doable at home..

It’s quite possible that would be the only difference between them and you. CO2 can increase yield dramatically. They run co2 around 1,200 PPM.

co2 can help but you can grow just as good. The biggest thing they have going for them is space which most home growers are limited to by. Lights are of of course a big factor, spectrum, intensity, etc. You can't just throw all the light you can at a plant though, this is where co2 comes in. Without co2 the plant can't handle higher ppfd, you want a minimum of 1000-1200 to start introducing co2 and you need a sealed room. The co2 bags and buckets are a waste IMO. It's really about keeping proper conditions, good ventilation, proper nutrients, plant training, etc. You will need to start experimenting a little with different nutrients, soils/medium, grow styles, etc to try and find what works best for you and the outcome you're looking for. Plus it's fun trying new things and making little changes here and there. You may want to research and grow strains that are known to produce dense buds.