Conventional detergents come ready to use: you buy them, go home and use them as they are, without having to worry about anything.
Since they contain a high percentage of water (often more than 80%), one day someone got the idea that the water content could be reduced and so the first concentrated detergents were born. We started seeing them popping up everywhere but especially for dishwashers and washing machines, with the mantra "you can use half a scoop instead of a whole one".
The next step was to take this mechanism to extremes, trying to remove all - or almost all - of the water contained: this is how the super-concentrated detergents were born, whose most common representatives are powders, tablets and pods for washing machines and dishwashers.
But what are the advantages and disadvantages of this type?
Advantages: less water = less weight, and therefore less effort
Ok, now I'm going to state the obvious but bear with me.
When you take water away from a detergent, you take away a part of the detergent that is "not needed" (it has no cleaning capacity) but it does have weight. The net effect is that the dose needed (i.e., the amount recommended by the manufacturer to achieve the expected result) weighs less. So, for example, if before I could do, let’s say, 50 washes with 2 L of laundry detergent now I will need maybe 1 L to do the same number of washes. So, for the same result, I saved 1 kilo of effort.
So less water = less weight, and less weight = less effort for us, which is not to be underestimated when we are getting home in the evening with our work bag, gym bag and dry cleaning and we also have to stop for groceries.
More importantly, this also means less effort for the truck that had to haul those detergents to the grocery store, so less emissions. Yayyy!
These positive effect increases as you reduce the amount of water in the detergent, peaking for super-concentrates, for which the amount of water is practically zero. We can also note that, in this case, the product is essentially dry, so no need for bottles to contain it. If you'd like to know more, I've delved into the subject by describing the various types of super-concentrates here.
So, at first glance, you could say that there are no disadvantages to switching from a ready-to-use detergent to a concentrated one: better for our back, better for the environment. Win-win!
In reality, what happens (and here we get into the behavioral psychology of all of us) is that, even though we are dealing with a concentrate, we all tend to fill the tubs as if it were not: "if there is space, I must fill it".
So we end up overdosing the detergent, polluting more and spending more. If we don't have a dispenser at home, it is therefore really important to be super aware of this mechanism and pay attention to it, otherwise we end up shooting ourselves in the foot.
This is where super-concentrated detergents in pods or tablets come in handy, because they are pre-dosed. On the other hand, the lack of water has its own drawbacks: the surfactants commonly used in liquid detergents have a hard time dissolving in the conditions in which we would dissolve super-concentrates at home (cold or moderately hot water, little agitation), so either you choose other types of surfactants and make more soluble through a bit of chemistry, or we are content to have a little less than the ready to use.